An IMAP Client for R


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. The aim of this package is to pave the way for email data analysis in R. To do so, mRpostman makes extensive use of the {curl} package and the libcurl C library.

mRpostman’s official website:


  1. In version, mRpostman went trough substantial changes, including ones that have no backward compatibility with versions <= 0.3.1. A detailed vignette on how to migrate your mRpostman’s deprecated code to the new syntax is available at “Migrating old code to the new mRpostman’s syntax”.

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


There are two ways of connecting to your IMAP server: using plain or OAuth2.0 authentication. Here, we only describe the plain authentication process. If you want to use OAuth2.0 authentication, please read the aforementioned vignette.

Allowing less secure apps access

When using plain authentication, most of the mail providers will require the user to enable less secure apps access. Once it is done, you will be able to access your mailbox using a “third party app” as mRpostman.

Plain authentication

Before using mRpostman, it is essential to configure the access to your email account. Various mail providers require that you enable “less secure apps” access to accept plain authentication between the IMAP server and a third-party app.

Let’s see how to configure simple plain authentication for Gmail, Yahoo Mail, AOL Mail, Hotmail, and Office 365.

Outlook - Office 365

There is no need to execute any external configuration. Please, note that the url parameter in configure_imap() should be set as url = "imaps://", and the username should be set as


There is no need to execute any external configuration. Please, note that the url parameter in configure_imap() should be set as url = "imaps://", and the username should be set as


1) Go to the Gmail website and log in with your credentials.

2) Then, go to

3) Set “Allow less secure apps” to ON.

Yahoo Mail

1) Go to the Yahoo Mail website and log in with your credentials.

2) Click on “Account Info”.

3) Click on “Account Security” on the left menu.

4) Then, set “Allow apps that use less secure sign in” ON

AOL Mail

1) Go to the AOL Mail website and log in with your credentials.

2) Click on “Options” and then on “Account Info”.

3) Click on “Account Security” on the left menu.

4) After, set “Allow apps that use less secure sign in” ON


From version onward, mRpostman is implemented under the OO paradigm, based on an R6 class called ImapCon. Its derived methods, and a few independent functions enable the R user to perform a myriad of IMAP commands.

The package is divided in 8 groups of operations. Below, we present all the available methods and functions:

  • configuration methods: configure_imap(), reset_url(), reset_username(), reset_password(), reset_verbose(), reset_use_ssl(), reset_buffersize(), reset_timeout_ms(), reset_xoauth2_bearer();
  • server capabilities method: list_server_capabilities();
  • mailbox operations methods: list_mail_folders(), select_folder(), examine_folder(), rename_folder(), create_folder(), list_flags();
  • single-search methods: search_before(), search_since(), search_period(), search_on(), search_sent_before(),search_sent_since(), search_sent_period(), search_sent_on(), search_string(), search_flag(), search_smaller_than(), search_larger_than(), search_younger_than(), search_older_than();
  • the custom-search method and its helper functions: search();
  • fetch methods: fetch_body(), fetch_header(), fetch_text(), fetch_metadata(), fetch_attachments_list(), fetch_attachments();
  • attachments methods: list_attachments(), get_attachments(), fetch_attachments_list(), fetch_attachments();
  • complementary methods: copy_msg(), move_msg(), esearch_min_id(), esearch_max_id(), esearch_count_msg(), delete_msg(), expunge(), add_flags(), remove_flags(), replace_flags().


# CRAN version

# Dev version
if (!require('remotes')) install.packages('remotes')

Basic Usage

1) Configure an IMAP connection and list the server’s capabilities


# Outlook - Office 365
con <- configure_imap(url="imaps://",

# other IMAP providers that were tested: Hotmail ("imaps://"),
#  Gmail (imaps://, Yahoo (imaps://, 
#  AOL (imaps://, Yandex (imaps://

# Other non-tested mail providers should work as well


2) List mail folders and select “INBOX”

# Listing

# Selecting
con$select_folder(name = "INBOX")

3) Search messages by date

res1 <- con$search_on(date_char = "02-Jan-2020")


4) Customizing a search with multiple criteria

Executing a search by string:

# messages that contain either "" OR "" in the "TO" header field
res2 <- con$search(OR(
  string(expr = "", where = "TO"),
  string(expr = "", where = "TO")


5) Fetch messages’ text using single-search results

res3 <- con$search_string(expr = "Welcome!", where = "SUBJECT") %>%
  con$fetch_text(write_to_disk = TRUE) # also writes results to disk


6) Attachments

You can list the attachments of one or more messages with:

1) the list_attachments() function:

con$search_since(date_char = "02-Jan-2020") %>%
  con$fetch_text() %>% # or with fetch_body()
  list_attachments() # does not depend on the 'con' object

… or more directly with:

2) fetch_attachments_list()

con$search_since(date_char = "02-Jan-2020") %>%

If you want to download the attachments of one or more messages, there are also two ways of doing that.

1) Using the get_attachments() method:

con$search_since(date_char = "02-Jan-2020") %>%
  con$fetch_text() %>% # or with fetch_body()

… and more directly with the

2) fetch_attachments() method:

con$search_since(date_char = "02-Jan-2020") %>%

Future Improvements

  • add further IMAP features;
  • eliminate the {stringr} dependency in REGEX;
  • implement a progress bar in fetch operations;

Known bugs

  • search results truncation: This is a libcurl’s known bug which causes the search results to be truncated when there is a large number of message ids returned. To circumvent this problem, you can set a higher buffersize value, increasing the buffer capacity, and verbose = TRUE for monitoring the server response for truncated results when executing a search. When possible, mRpostman tries to issue a warning for possible truncated values.

  • verbose = TRUE malfunction on Windows: This seems to be related to the {curl} R package. When using the verbose = TRUE on Windows, the flow of information between the IMAP server and the R session presents an intermittent behavior, which causes it to not be shown on the console, or with a considerable delay.

  • shared mailbox access not working: This seems to be another libcurl’s bug, although more tests need to be done to confirm it. It does not allow the user to connect to a shared mailbox. To circumvent this, if the shared mailbox has a password associated with it, you can try a direct regular connection.

  • xoauth2_bearer SASL error: This is related to old libcurl’s versions which causes the access token to not be properly passed to the server. This bug was fixed in libcurl 7.65.0. The problem is that many Linux distributions, such as Ubuntu 18.04, still provide libcurl 7.58.0 in their official distribution (libcurl4-openssl-dev). If you use a newer Linux distro such as Ubuntu 20.04, you should be fine as the distributed libcurl’s version will be above 7.65.0. Another alternative is to use plain authentication instead of OAuth2.0.


This package is licensed under the terms of the GPL-3 License.


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

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.

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

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