mRpostman basics

Introduction

mRpostman is an easy-to-use IMAP client that provides tools for message searching, selective fetching of message attributes, mailbox management, attachment extraction, and several other IMAP features, paving the way for email data analysis in R. To do so, this package makes extensive use of the {curl} package and the libcurl C library.

In this vignette, we present all available methods and functions of this package, but not all the possibilities one can explore.

IMPORTANT:

0. In 2026 the package went through a deep refactoring, released as version 3.0.0. Everything written for 1.x/2.x keeps working, but four things changed for the better: (i) query() is now the canonical way to search - every search_*() method and the AND()/OR() combinators keep working as soft-deprecated spellings (they warn once per session); (ii) attachments have a consolidated API - attachments(), attachments_manifest(), and extract_attachments(); (iii) use_uid, mute, and retries can be set once, in configure_imap(), as connection-level defaults - and use_uid now defaults to TRUE (UIDs are stable; sequence numbers renumber on expunge; set use_uid = FALSE to restore the old behavior); (iv) failures are classed conditions (e.g. mRpostman_server_error) that tryCatch() can handle by kind.

1. In version 0.9.0.0, mRpostman went through substantial changes, including ones that have no backward compatibility with versions <= 0.3.1. If you have code written with the deprecated syntax of versions <= 0.3.1, please refer to the package’s NEWS.md file for an overview of the changes introduced in 0.9.0.0.

2. Old versions of the libcurl C library ({curl}’s main engine) will cause malfunctioning of this package. If your libcurl’s version is above 7.58.0, you should be fine. If you intend to use OAuth 2.0 authentication, then you will need libcurl >= 7.65.0. To know more about the OAuth 2.0 authentication in this package, refer to the “Using IMAP OAuth2.0 authentication in mRpostman” vignette.

3. Most mail providers discontinued less secure apps access. If it is still available and you are comfortable with this type of access you can enable this option for your account on your mail provider. Some providers, such as Yahoo Mail, also offer the option to generate a password to be used by third-party apps such as mRpostman. The other option, as mentioned above, is to set up OAuth2 (two-factor authentication) in order to access your mailbox. Please also refer to the “Using IMAP OAuth2.0 authentication in mRpostman” vignette.

Providers and their IMAP urls

* For Office 365 accounts, the username should be set as [email protected] or [email protected] for example.

Package Structure

The package is now implemented under an OO framework, using an R6 class. The main functionalities of mRpostman are implemented as methods of the R6 class called ImapCon. There are also a few independent functions. All methods and functions are described below:

• configuration methods: configure_imap() (including the connection-level defaults use_uid, mute, and retries), reset_url(), reset_username(), reset_password(), reset_verbose(), reset_buffersize(), reset_timeout_ms(), reset_xoauth2_bearer();
• server-capabilities methods: list_server_capabilities(), has_capability();
• mailbox-operations methods: list_mail_folders(), select_folder(), examine_folder(), rename_folder(), create_folder(), list_flags();
• the search method: query() - an ordinary R expression, e.g. con$query((subject == "budget" | "budget 3") & flag != "SEEN");
• the custom-search method: search(), with the criteria constructors before(), since(), on(), sent_before(), sent_since(), sent_on(), string(), flag(), smaller_than(), larger_than(), younger_than(), older_than(), verbatim(), combined with R’s own &, |, and !;
• deprecated search spellings (they keep working, warning once per session): the search_*() single-criterion methods and the AND()/OR() combinators;
• fetch methods: fetch_body(), fetch_header(), fetch_text(), fetch_metadata();
• attachments: attachments_manifest() (list without downloading), attachments() (download, guided by the BODYSTRUCTURE), and the exported extract_attachments() (from already-fetched bodies); the pre-3.0.0 names remain as deprecated aliases;
• complementary methods: copy_msg(), move_msg(), esearch_min_id(), esearch_max_id(), esearch_count(), delete_msg(), expunge(), add_flags(), remove_flags(), replace_flags().

1) How do I start? (Connection configuration)

After setting the authentication method in your mail provider, you have to configure an IMAP connection:

library(mRpostman)

# IMAP settings

# Outlook - Office 365
con <- configure_imap(
  url="imaps://outlook.office365.com",
  username="user@your_company.com",
  password=rstudioapi::askForPassword()
  )

# Gmail
con <- configure_imap(
  url = "imaps://imap.gmail.com",
  username = "user",
  password = rstudioapi::askForPassword()
  )

# Hotmail
con <- configure_imap(
  url = "imaps://imap-mail.outlook.com",
  username = "[email protected]",
  password = rstudioapi::askForPassword()
  )

# Yahoo Mail
con <- configure_imap(
  url="imaps://imap.mail.yahoo.com/",
  username="your_user",
  password=rstudioapi::askForPassword()
  )

# AOL Mail
con <- configure_imap(
  url="imaps://export.imap.aol.com/",
  username="your_user",
  password=rstudioapi::askForPassword()
  )

# Yandex Mail
con <- configure_imap(
  url="imaps://imap.yandex.com",
  username="your_user",
  password=rstudioapi::askForPassword()
  )

# ... and any other mail provider with IMAP support

Other useful options are: timeout_ms, verbose = TRUE, buffersize. Further {curl} options related to IMAP functionalities can be passed to configure_imap(), but you probably won’t need it. See curl::curl_options().

Since version 0.9.0.0, this package provides more flexibility to the user in the sense that you can modify the connection parameters for specific commands or parts of a script, using the reset_*() methods. This prevents users from having to call configure_imap() multiple times during a session or in a script. It is particularly useful when the user is going to perform some fetch operation, for example. In this case, it is recommended to increase the timeout_ms and set verbose = FALSE.

The con object that we created in the example above has the ImapCon R6 class. Now, almost 99% of the other IMAP commands to be performed on the server will be called following the structure: con$method(). The exceptions are the list_attachments() function and the helper functions of the custom-search group.

As you will see, the R6 framework combined with {curl} will make this package work like a session-based IMAP client. Besides this, for some commands, users will be able to use the tidy approach with pipes. All this together provides an elegant way of accessing your IMAP provider, searching and fetching emails, and managing your mailbox as well.

Since 3.0.0, three arguments that used to be repeated on every call can be set once, as connection-level defaults: configure_imap(..., mute = TRUE, retries = 2) makes every method stay quiet and retry twice, unless a specific call overrides it. use_uid is one of them and now defaults to TRUE: UIDs are stable for the lifetime of a message, while sequence numbers renumber whenever messages are expunged; pass use_uid = FALSE (per connection or per call) if you need sequence numbers.

2) Server capabilities

Once the connection is configured, it is important to know which capabilities your IMAP provider offers to users. This impacts on which type of operations you are allowed to perform. For example, if your server has the WITHIN extension you can use the WITHIN search methods search_younger_than() and search_older_than(); if the server has the ESEARCH capability, besides being allowed to use the esearch_*() methods, you can optimize all your search functions with the esearch = TRUE parameter; if you see the MOVE capability, then you can use the move_msg() method. Therefore, to know all your server capabilities, you can use list_server_capabilities.

con$list_server_capabilities()

3) Mailbox commands

con$list_mail_folders()

con$create_folder(folder = "New Folder")

con$select_folder(folder = "INBOX")

con$select_folder(folder = "Inbox")

con$examine_folder()

con$examine_folder(folder = "Sent")

con$select_folder(folder = "CRAN Messages")

con$rename_folder(new_name = "CRAN")

con$rename_folder(folder = "Sent", new_name = "Sent2")

con$list_flags()

con$delete_folder(folder = "Old Folder")

con$subscribe_folder(folder = "INBOX")

con$unsubscribe_folder(folder = "INBOX")

con$list_subscribed_folders()

con$status(folder = "INBOX")

# or only some items, for the currently selected folder:
con$select_folder("INBOX")
con$status(items = c("MESSAGES", "UNSEEN"))

con$list_special_use_folders()

con$namespace()

con$get_quota_root(name = "INBOX")

# or, for a known quota root:
con$get_quota(quota_root = "")

con$select_folder("INBOX")

con$close_folder()      # closes and expunges \Deleted
# or:
con$unselect_folder()   # closes without expunging

con$id()

# optionally disclosing the client id:
con$id(fields = c(name = "mRpostman", version = "1.2.1"))

4) Single-search (deprecated spellings)

NOTE (3.0.0): every search in this section has a direct spelling in the canonical query() interface of Section 9 - e.g. con$search_before(date_char = "02-Jan-2020") is con$query(date < "2020-01-02"). The methods below keep working, but signal a deprecation warning once per session.

All search methods will return a numeric vector containing the results from the search. This allows users to chain fetch operations together with search one. You can also NEGATE all search expressions by setting negate = TRUE.

If your server supports ESEARCH, we recommend you to use it. It will prevent your results from being truncated when there are too many message ids and you didn’t set a high buffersize in configure_imap()¹. With “ESEARCH”, the results will be condensed to groups of sequences similar to what does. For instance, if your search returns 10000 results, it is better to have condensed groups such as 1:10, 12, 23:27, ... instead of a sequence of 1, 2, 3, 4, 5, 6, ..., 10, 12, 23, 24, 25, .... If you can’t use ESEARCH, or if your results are being truncated even with ESEARCH, you can try to increase your buffersize in configure_imap() to avoid this.

con$select_folder(folder = "INBOX")

res <- con$search_before(date_char = "07-Sep-2020")

res

res <- con$search_before(date_char = "07-Sep-2020",
                         use_uid = TRUE,
                         flag = c("ANSWERED", "SEEN"))

res

res <- con$search_before(date_char = "07-Sep-2020",
                         use_uid = TRUE,
                         flag = c("ANSWERED", "SEEN"),
                         esearch = TRUE)

res

res <- con$search_before(date_char = "07-Sep-2020",
                         negate = TRUE,
                         use_uid = TRUE)
                         
res

res <- con$search_since(date_char = "07-Sep-2020",
                        use_uid = TRUE)
                         
res

res <- con$search_period(since_date_char = "02-Jan-2020",
                         before_date_char = "30-Jun-2020")
                         
res

res <- con$search_period(since_date_char = "02-Jan-2020",
                         before_date_char = "30-Jun-2020",
                         negate = TRUE)
                         
res

con$search_on(date_char = "02-Jan-2020")

con$search_sent_before(date_char = "07-Sep-2020")

res <- con$search_sent_before(date_char = "07-Sep-2020",
                              negate = TRUE,
                              use_uid = TRUE,
                              flag = c("ANSWERED", "SEEN"))

res

con$search_sent_since(date_char = "07-Sep-2020")

con$search_sent_period(since_date_char = "02-Jan-2020",
                       before_date_char = "30-Jun-2020")

con$search_sent_on(date_char = "30-Jun-2020")

con$select_folder(folder = "K-State")

con$search_string(expr = "[email protected]", where = "TO")

con$search_string(expr = "[email protected]", where = "FROM")

con$search_string(expr = "PhD offer", where = "SUBJECT")

con$search_string(expr = "Dear Allan" where = "TEXT")

con$search_string(expr = "Dear Allan" where = "BODY")

con$search_flag(name = c("ANSWERED", "Seen"), use_uid = TRUE)

con$search_smaller_than(size = 512000) # smaller than 512KB

con$search_larger_than(size = 512000) # larger than 512KB

con$search_younger_than(seconds = 3600) # msgs received less than one hour (3600 sec)

con$search_older_than(seconds = 3600) # msgs received more than one hour ago (3600 sec)

con$select_folder(folder = "INBOX")

# most recent first:
con$sort(by = "DATE", reverse = TRUE)

# sort a restricted set (search criteria) by sender:
con$sort(by = "FROM", criteria = "SINCE 01-Jan-2020")

con$select_folder(folder = "INBOX")

con$thread(algorithm = "REFERENCES")

5) Custom-search

The search() method and its helper functions enable users to create a vast number of complex and customized search requests by combining different criteria, using all the types of searches previously presented in this document.

These are the helper functions you can use inside search():

1. Relational operators: R’s own &, |, and ! (the AND() and OR() helpers keep working, but are deprecated since 3.0.0); 2) Criteria definition: before(), since(), on(), sent_before(), sent_since(), sent_on(), string(), flag(), smaller_than(), larger_than(), younger_than(), and older_than().

NOTE: IMAP queries follow Polish notation, i.e. operators such as OR come before arguments, e.g. “OR argument1 argument2”. Therefore, the relational operators functions in this package should be used like the following examples: OR(before(date_char = "17-Apr-2015"), string(expr = "Jimmy", where = "FROM")). Even though there is no “AND” operator in the IMAP protocol, this package adds a helper function AND() to indicate multiple arguments that must be searched together, e.g. AND(since(date_char = "01-Jul-2018"), larger_than(size = 16000)).

Example 1: Searching for messages (in “INBOX”) containing the string “Kansas State University” in the “SUBJECT” header field AND that were received before “02-Jan-2020”.

con$select_folder(folder = "INBOX")


res <- con$search(request = AND(string(expr = "Kansas State University", where = "SUBJECT"),
                                before(date_char = "02-Jan-2020")))

res

Example 2: Searching (using UID) for messages received from “@k-state.edu” OR “@ksu.edu”.

con$search(request = OR(string(expr = "@k-state.edu", where = "FROM"),
                        string(expr = "@ksu.edu", where = "FROM")),
           use_uid = TRUE)

6) Fetch

You can fetch the full content of messages, or their parts, such as the header, text, or specific metadata fields. Besides this, you can also fetch a message attachments list or the attachment files themselves, downloading them to the disk.

We usually fetch messages after a search operation. Given the output of the search functions in mRpostman, you can use the pipe %>% to chain the search and the fetch operations together. Using the base R approach is perfectly possible as well.

In the main fetch methods (those that are not related to attachment fetching), you can choose to write the fetch results to disk (working directory) using write_to_disk = TRUE. If you opt to do so, mRpostman saves the fetched content to a .txt file in the following folder structure: working directory > imap.server.url > mail folder name. The text files will be named after the id of the fetched message. If the operation was executed using the UID, the “UID” prefix is added to the file names.

IMPORTANT:

1. If the fetch operation is to be chained after a search, the use_uid arguments in the two operations have to be the same. Otherwise, an error will occur or the fetch will be performed on wrong messages’ ids.

2. It is always recommended to increase the timeout_ms before fetch_body(), fetch_text(), and fetch_attachments() operations as sometimes the operation may hang for a few seconds while fetching the message parts.

3. if you have configured a connection with verbose = TRUE, it is extremely recommended that you reset it to FALSE before a fetching operation. The verbose = TRUE option fills the console with the whole flux of information between the server and the client, drastically slowing the speed of the process and your R session.

# increasing timeout_ms
con$reset_timeout_ms(x = 30000) # ... to 30 secs

# and supposing that you had verbose = TRUE before
con$reset_verbose(x = FALSE)

# tidy approach
con$search_string(expr = "@k-state.edu", where = "FROM") %>%
  con$fetch_body(write_to_disk = TRUE, keep_in_mem = FALSE)

# ---------------

# base R approach
res <- con$search_string(expr = "@k-state.edu", where = "FROM")

con$fetch_body(msg_id = res, write_to_disk = TRUE, keep_in_mem = FALSE)

# tidy approach
out <- con$search_since(date_char = "15-Aug-2019", use_uid = TRUE) %>%
  con$fetch_header(use_uid = TRUE, fields = c("DATE", "SUBJECT"))

out

# ---------------

# base R approach
res <- con$search_since(date_char = "15-Aug-2019", use_uid = TRUE)

out <- con$fetch_header(use_uid = TRUE, fields = c("DATE", "SUBJECT"))

out

con$search_since(date_char = "15-Aug-2019") %>%
  con$fetch_text(write_to_disk = TRUE, keep_in_mem = FALSE)

out <- con$search_on(date_char = "15-Aug-2019", use_uid = TRUE) %>%
  con$fetch_metadata(use_uid = TRUE, attribute = c("INTERNALDATE", "UID", "ENVELOPE"))

7) Attachments

Since 3.0.0 the attachment family has three entry points: two methods that talk to the server, and one exported function that works offline on messages you already fetched. (The pre-3.0.0 names - fetch_attachments_list(), fetch_attachments(), fetch_attachment_parts(), get_attachments(), and list_attachments() - keep working as deprecated aliases.)

con$attachments_manifest(con$query(size > 1e6))

manifest <- con$query(subject == "report" & flag != "SEEN") %>%
  con$attachments(dest = "~/attachments")
manifest # one row per file: id, part, filename, type, size, path

out <- con$query(size > 1e6) %>% con$fetch_body()
extract_attachments(out)                        # report only
extract_attachments(out, dest = "~/attachments")  # write the files

8) Complementary operations

Here we present other functions to perform very useful complementary IMAP operations.

con$select_folder(folder = "INBOX")

con$search_since(date_char = "10-may-2019") %>%
  con$copy_msg(folder = "K-State")

con$esearch_min_id(flag = c("Answered", "Seen"))

con$esearch_min_id(flag = c("Answered", "Seen"))

con$esearch_count(flag = c("Answered", "Seen"))

con$select_folder(folder = "Trash")

con$search_before(date_char = "10-may-2012") %>%
  con$delete_msg()

con$delete_msg(msg_id = 66128)

# expunge the entire mail folder
con$expunge()

# expunge selected msg UID
con$delete_msg(msg_id = 71171, use_uid = TRUE) %>%
  expunge()

con$select_folder(folder = "INBOX")

con$search_since(date_char = "01-Sep-2020", use_uid = TRUE) %>%
  con$add_flags(flags_to_set = "\\Answered", use_uid = TRUE)

con$search_since(date_char = "01-Sep-2020", use_uid = TRUE) %>%
  con$replace_flags(flags_to_set = c("\\Seen", "\\Flagged", use_uid = TRUE)

con$search_since(date_char = "01-Sep-2020", use_uid = TRUE) %>%
  con$remobe_flags(flags_to_unset = c("\\Seen", "\\Flagged", use_uid = TRUE)

con$search_on(date_char = "07-Sep-2020") %>%
  con$move_msg(folder = "K-State")

con$search_on(date_char = "07-Sep-2020") %>%
  con$copy_msg(folder = "K-State", reselect = FALSE) %>%
  con$add_flags(flags_to_set = "\\Deleted") %>%
  con$expunge()

con$noop()

msg <- paste("From: [email protected]",
             "To: [email protected]",
             "Subject: Hi",
             "",
             "Message body.",
             sep = "\r\n")

con$append_msg(message = msg, folder = "Drafts")

9) The query language (canonical since 3.0.0)

Since 2.3.0 a search can be written as an ordinary R expression. query() captures the expression unevaluated, translates it internally, through a pure function, into the same RFC 3501 search string, and executes it exactly like search():

con$query((subject == "budget" | "budget 3") & flag != "SEEN")
con$query(sent >= "2001-10-01" & sent < "2002-01-01" & size > 5e6, use_uid = TRUE)
con$query(subject %in% c("budget", "forecast") & age < 7 * 86400)

Fields: subject, from, to, cc, bcc, body, text (where == means contains, as the protocol defines), flag (system flags and custom keywords), size in bytes, age in seconds, the date fields sent, date (internal date), and saved (on SAVEDATE servers), and header("Name"). Comparisons combine with &, |, !, %in%, and parentheses, with R’s usual precedence; anything else, variables included, is evaluated in your environment. A bare string next to | or & inherits the field of the preceding comparison, which is what makes subject == "budget" | "budget 3" work. The criterion constructors of the previous section also gained the native operators: string("budget", where = "SUBJECT") & !flag("SEEN") is the current spelling of what AND() and negate = TRUE used to write. Since 3.0.0 this interface is the canonical one: the single-criterion search_*() methods and the AND()/OR() combinators remain available as deprecated spellings. Raw protocol fragments with no field of their own (Gmail’s X-GM-RAW, sequence sets, FUZZY) enter the language verbatim through verbatim().

10) Protocol extensions (since 1.5.0)

Versions 1.5.0 to 1.5.2 completed the IMAP4rev1 command set (CHECK) and added a set of optional extensions. Each one is checked against the server’s CAPABILITY response before the command is issued, so an unsupported extension fails with a message naming the command, its RFC, and list_server_capabilities(). The Docker sandbox (see the sandbox vignette) supports all of them.

uid <- con$append_msg(message = msg, folder = "Drafts", flags = "Draft")
ids <- con$copy_msg(msg_id = c(12, 15), use_uid = TRUE, folder = "Archive",
                    reselect = FALSE)
attr(ids, "copyuid")

con$list_folders_status(items = c("MESSAGES", "UNSEEN", "SIZE"))
con$list_mail_folders(detailed = TRUE)

con$search(request = AND(flag("UNSEEN"), sent_since(date_char = "01-Jan-2026")),
           save = TRUE)
previews <- con$fetch_preview(msg_id = "$")   # PREVIEW, RFC 8970
con$add_flags(msg_id = "$", flags_to_set = "\\Seen")

last <- con$status(items = "HIGHESTMODSEQ")[["HIGHESTMODSEQ"]]
# ... in a later session:
changed <- con$search(request = modseq(last + 1))

con$sort(by = "SIZE", reverse = TRUE, return = c("COUNT", "MAX"))

con$my_rights(folder = "INBOX")
con$set_acl(name = "Shared", identifier = "user=bob", rights = "lrs")
con$get_acl(folder = "Shared")

11) A second connection for IDLE and MULTIAPPEND (since 2.0.0)

Two operations cannot be expressed as one libcurl request: IDLE (RFC 2177), which parks the connection while the server pushes notifications, and commands that carry several literals, such as MULTIAPPEND (RFC 3502). For them, mRpostman opens a second, dedicated connection through libcurl’s CONNECT_ONLY mode (libcurl still performs the TLS handshake and certificate verification) and speaks IMAP directly on that socket. The main connection stays free.

idle() waits until something happens in the folder, or until timeout seconds elapse, and returns the events the server announced. A callback can stop the wait early, and the main connection can then fetch what arrived:

con$select_folder("INBOX")
ev <- con$idle(timeout = 600, callback = function(ev) !any(ev$type == "EXISTS"))
if (any(ev$type == "EXISTS")) {
  con$fetch_envelope(msg_id = max(ev$id[ev$type == "EXISTS"]))
}

append_msgs() uploads several messages in one command when the server advertises MULTIAPPEND, and one append_msg() at a time otherwise:

msgs <- vapply(1:3, function(i) paste0("Subject: m", i, "\r\n\r\nbody ", i, "\r\n"), "")
uids <- con$append_msgs(msgs, folder = "Archive", flags = "Seen")

Since 2.1.0 the same layer serves notify() (RFC 5465: events for several folders at once), fetch_binary() (RFC 3516: attachments decoded by the server), append_catenate() (RFC 4469: a message assembled on the server from imap_url() parts and new text), and, on every one of them, compress = TRUE (RFC 4978):

ev <- con$notify(mailboxes = "personal", timeout = 600)      # STATUS lines for any folder that changes
pdf <- con$fetch_binary(msg_id = 3, part = "2")              # bytes, already decoded by the server
con$append_catenate(parts = list("Subject: Fwd\r\n\r\n", imap_url("INBOX", uid = 12, section = "TEXT")),
                    folder = "Archive")

Version 2.2.0 closes the sweep of the IANA capability registry. On servers that advertise the corresponding capability, sort(by = "DISPLAYFROM") (RFC 5957), thread(algorithm = "REFS"), and esearch_partial() (paged searching, RFC 9394 / RFC 5267) become available, while non-synchronizing literals (RFC 7888) and the APPENDLIMIT guard (RFC 7889) are applied automatically. The remaining registered capabilities are covered by experimental methods – esort_partial(), replace_msg(), fetch_objectid(), uid_batches(), esearch_multi(), unauthenticate(), language(), comparator(), genurlauth(), urlfetch(), fetch_convert(), fetch_annotation(), store_annotation(), and the fuzzy() and filter_stored() search criteria – which follow the RFC grammars but could not be exercised against a live server, since no widely deployed server advertises those capabilities.

The second connection needs the credentials again: they are kept in a private field of the connection object (never printed, not part of con_params) and cleared by disconnect(). TLS works as on the main connection: an imaps:// URL, or use_ssl = TRUE on an imap:// URL, in which case the second connection is upgraded with STARTTLS before any command is sent.

References

Babcock, N. (2016), Introduction to IMAP, Blog, May 2016, http.

Crispin, M. (2003), INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1, RFC 3501, March 2003, http.

Crispin, M. and Murchison, K. (2008), Internet Message Access Protocol - SORT and THREAD Extensions, RFC 5256, June 2008, http.

Gahrns, M. and Newman, C. (2003), IMAP4 Namespace, RFC 2342, May 2003, http.

Leiba, B. and Melnikov, A. (2011), IMAP LIST Extension for Special-Use Mailboxes, RFC 6154, March 2011, http.

Myers, J. (1997), IMAP4 QUOTA extension, RFC 2087, January 1997, http.

Showalter, T. (2003), IMAP4 ID extension, RFC 2971, October 2000, http.

Melnikov, A. (2004), Internet Message Access Protocol (IMAP) UNSELECT command, RFC 3691, February 2004, http.

Freed, N. and Borenstein, N. (1996), Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types, RFC 2046, November 1996, http.

Gungor, A. (2018), Using IMAP Internal Date for Forensic Email Authentication, Articles, Forensic Focus, http.

Heinlein, P. and Hartleben, P. (2008). The Book of IMAP: Building a Mail Server with Courier and Cyrus. No Starch Press. ISBN 978-1-59327-177-0.

Resnick, P. (2001), Internet Message Format, RFC 2822, April 2001, http.

Resnick, P. (2008), Internet Message Format, RFC 5322, October 2008, http.

Ooms, J. (2020), curl: A Modern and Flexible Web Client for R. R package version 4.3, http.

Stenberg, D. Libcurl - The Multiprotocol File Transfer Library, http