WP Mailster


True two-way group communication over email

Allow your users to be part of a group and communicate by email without having to log into a website.
Similar to programs like Mailman or Listserv this plugin allows you to run a discussion mailing list.

That means that every email sent to a central email address is forwarded to the rest of the members of the list.
When members reply to such emails WP Mailster again forwards them to the other list recipients.
Unlike newsletter plugins this allows true two-way communication via email.

Features include:

  • group communication through email
  • usable with any POP3/IMAP email account
  • recipients can be managed in the WordPress admin area
  • users can subscribe/unsubscribe through widgets on the website
  • all WP users can be chosen as recipients, additional recipients can be stored (without having to create them as WP users)
  • users can be organized in groups
  • single users or whole groups can be added as recipients of a mailing list
  • replies to mailing list messages can be forwarded to all recipients (or only the sender)
  • email archive for browsing the mails
  • full support of HTML emails and attachments
  • custom headers and footers
  • subject prefixes
  • many more features

Note: This version of WP Mailster is FREE and limited in terms of number of lists and subscribers per list. Additional features such as captcha protection, double opt-in, email filtering, configurable event notifications, and many others are available in the premium editions.


  • The dashboard provides an overview of the overall status (mailing list, #emails etc)
  • All emails (that are forwarded to the subscribers) are also stored in an email archive in the admin section
  • Mailing list settings, general settings
  • Mailing list settings, mailbox (incoming email)
  • Mailing list settings, mailbox: choose from some pre-configured servers or use your own (what most users do)
  • Mailing list settings, sender settings (outgoing email)
  • Mailing list settings, mail content
  • Mailing list settings, list behaviour
  • Manage your recipients (per list and/or via custom groups)
  • Add members to your list (both WP users and users outside WP are possible)


How do I send an email?

When you want to use WP Mailster you don’t need to browse to a website, login and do something to send the message there – you just use your favorite mail client.
Simply write an email to the mailing list’s address – and nothing else. So use Gmail, Outlook, Thunderbird, a Webmailer, any way you like – just send it to the mailing list address you have setup in WP Mailster.

Why take the emails so long to be delivered? How can I speed up sending?

WP Mailster is a part of WordPress which is a PHP based web application. That means: it can not act/run without being triggered and it can not run forever when triggered. This is a technical limitation coming from PHP, not from WP Mailster or WordPress.
Triggering means that somebody accesses the site. During the page load WP Mailster is handling the jobs to do (mail retrieving/sending). Thus mails can only be send/retrieved when somebody is browsing your site, otherwise the delivery is delayed or never done. As your site might not be browsed every few minutes 24×7 we recommend you to use a cronjob that opens the site periodically. We have a guide on our website on how to set that up.

What are send errors?

The send errors are messages your email server is giving back to WP Mailster basically saying “I will not forward this message”. Then WP Mailster sending for some time but eventually stops which is what you see happening.
The cause can be a lot of things, e.g. hitting send limits (per hour/day) or sending email with content that the server does not like.
You need to find out what your email servers are telling WP Mailster. Please follow our troubleshooting guide on our site.


February 18, 2023
We are a small non profit org (choir). After we changed our Webhosting Provider we suddenly faced the issue, that we produce too much emails / hour somtimes: When discussions via email come up within a group of 40 people this sums up fast and the webhosting is somewhat restrictive. We had six distribution lists with forwarding to members individual mail addresses. We looked for a better solution, which allows unlimited mail sending. Now we are using WP Mailster and it does the job as we need it. The option to have both Wordpress Users and users created directly in the plugin assigned to groups or mailinglists is great and saves some time. Also self-signup is useful and the added layer of security (e.g. only list members are allowed to send to the list) is an improvement compared to our legacy setup. We are using Amazon Simple Email Service via SMTP to send emails coming from WP Mailster. I had some trial and error to identify the correct SMTP setup, but finally it works. I sent the setup to the author, so it can go to the list of provider settings, which the author published on the plugin website.
February 2, 2023
I've been working with WP Mailster for a little time, doing quite a lot of research before deploying it to my clients. I find the plugin to be sound and stable and the feature set is what you expect from a good Mail List Server. The shortcodes are very useful and help to quicken the development work. I do like the fact that the parameters are "per user list" and not just global - makes a lot of difference. I used listserv back in the Unix days and have trying to find a plugin with that simplicity and power for a long time - WP Mailster fits the bill. I've had occaision to use their support for problems and development questions. Very happy with the support indeed. Swift and helpful. I would be very happy to recommend WP Mailster to anyone who wants a good straightforward listserv plugin.
December 16, 2022
We've been using WP-Mailster for about 2 years. During that time we've encountered various issues that caused the plugin to fail or not not perform entirely as expected because of local server setup issues . Each time the WP-Mailster staff worked diligently to resolve our issues. We ran into another problem this month and once again they stepped up. No software runs entirely trouble free so it's nice to have support that is there for you.
November 24, 2022 1 reply
About 7 years ago I searched for a ListServ application to be used on a WordPress membership site --- I could not find one other than the Joomla version of this plugin. Using a sub-domain and the Joomla platform, it did its job flawlessly for the last 6 or 7 years. For this period, I manually had to synchronize the WordPress membership with the Joomla database. Now, as with any other software, I rebuild and updated the WordPress membership website to WordPress 6.1, updated the server to PHP 8.1. and installed the WordPress version WP Mailster (enterprise, because I need a license for a second website) and ditched the old Joomla based mail list server. It was an effortless crossover. WP Mailster does what it is intended for, its interfaces are logical and support is given speedily. The best part, no third party is involved to disseminate the emails.
January 27, 2022
This plugin is very feature-rich and powerful. It is really one of the only ones of its kind. I had a couple of issues when configuring it and testing it, but I received very fast and helpful replies from support. The plugin is perfect for many usage cases. Mine is simply that I have a WordPress website that used to use Google Groups. Google Groups is great, but everyone needs to have a Google account to access the web-based interface. Also, there is no easy way to sync Google Groups membership with your website's member data. Trust me, I have tried, but none of them work very well. Thanks to the developer for this great creation! Keep up the nice work.
January 7, 2022
We have run Listservs on two member association websites for 7 years. We have used outside/non-wordpress vendors. We have used and tested other Wordpress plugins. We even built our own Wordpress solution that worked for us for a while. We've been working with WP Mailister now for about a year, and it has been by far the best solution for us. Simple set up. All of the options and features we could ever need. Excellent support and customer service. Comprehensive documentation. And it's so affordable. For the users, it is simple to use, and we love having the user-facing email archive. I would highly recommend this plugin if you're looking for a Wordpress listserv solution.
Read all 24 reviews

Contributors & Developers

“WP Mailster” is open source software. The following people have contributed to this plugin.


“WP Mailster” has been translated into 2 locales. Thank you to the translators for their contributions.

Translate “WP Mailster” into your language.

Interested in development?

Browse the code, check out the SVN repository, or subscribe to the development log by RSS.



Release Date – June 6th, 2023

  • [Bug Fix] When formatted HTML with very long lines are encountered, the automatic line splitting may run into issues. e.g. when formatted Text from Google Docs is copied into email body. This is now fixed.
  • [Bug Fix] Fix subscriber module problem with PHP 8.1/8.2
  • [Bug Fix] Anticipate problems with apostrophes and quotes characters being part of users’ names and notes
  • [Bug Fix] Do not log to PHP error log during installation
  • [Bug Fix] Remove unneeded code, no need to require parse_ini_file function


Release Date – March 29th, 2023

  • [Feature] Add removeFromGroup option for unsubscribe forms to automatically remove a user from a user group when the user unsubscribes
  • [Improvement] Warn about system incompatibility issues (like missing PHP IMAP extensions)
  • [Improvement] Default order lists, users and names by name
  • [Bug Fix] Fix timezone issue for email received and forwarded timestamps
  • [Bug Fix] Fix for iPhone embedded images/fotos
  • [Bug Fix] Fix: date parts (like month names) are translated
  • [Bug Fix] User interface for adding mailing list(s) is now tabbed again
  • [Bug Fix] User interface (select list of group users) works correctly after new group was created
  • [Bug Fix] Avoid PHP warnings


Release Date – February 8th, 2023

  • [Bug Fix] Fix PHP include problem related to library Html2Text in free edition as well
  • [Bug Fix] Sender (SMTP) connection check feedback working again
  • [Bug Fix] Avoid some PHP warnings in PHP 8.x


Release Date – February 2nd, 2023

  • [Bug Fix] Email without TO recipient will not stop email(s) from being retrieved from mailing list inbox
  • [Bug Fix] Fix PHP include problem related to library Html2Text (and others)
  • [Bug Fix] The add2Group parameter works in the subscribe-shortcode
  • [Bug Fix] Ability to deal with charset collation differences (between WP users and WP Mailster database tables)
  • [Bug Fix] Avoid PHP warnings in PHP 8.1


Release Date – January 9th, 2023

  • [Improvement] Better warn about non-supported special characters in the mailing list password(s)
  • [Improvement] UI improvements (show attachment indicator in email archive, explain fwd errors/completed indicators)
  • [Improvement] Add list name in List-Subscribe / List-Unsubscribe headers (subject lines)
  • [Bug Fix] Fix issue when no iconv functionality is available for charset conversion
  • [Bug Fix] Fix PHP errors (PHP 8)
  • [Bug Fix] Saving WP user’s lists/groups will not cause incorrect error message
  • [Bug Fix] Do not show current date/time in send timestamp column when sending was not done
  • [Bug Fix] Fix some language typos


Release Date – October 20th, 2022

  • [Improvement] For address mode = TO (single recipient per email), pre-fill email address in unsubscribe links
  • [Improvement] Stop using $_SESSION to avoid problems with WP health check etc.
  • [Improvement] Introduce various filters for altering the subscribe/unsubscribe endpoints headers, text and buttons
  • [Improvement] Introduce filter wpmailster_email_processing_attachment_default_filename to override default attachment filename (mst_no_filename) if needed
  • [Bug Fix] Subscribe and unsubscribe dialogs can now be translated
  • [Bug Fix] Fixed unsubscribe problem: when for one email address, there is a both a WordPress and a WP Mailster user, both get unsubscribed
  • [Bug Fix] License key can be saved in WP Mailster settings if ad-hoc check/validation fails
  • [Bug Fix] Change license backend callbacks to be executed server side (to avoid issues with CSP / Content Security Policy blocking in browsers)
  • [Bug Fix] Remove several PHP notices


Release Date – August 23rd, 2022

  • [Improvement] Store log file now in wp-content/uploads/wp-mailster directory to avoid problems on plugin updates/upgrades/downgrades
  • [Bug Fix] mst_emails shortcode’s list ID (lid) filter works again
  • [Bug Fix] Goodbye/welcome messages were not sent in some situations where admin changed list memberships
  • [Bug Fix] Support special characters in passwords (slash, “/”, was missing)


Release Date – July 27th, 2022

  • [Improvement] Update minimal system requirements to WP 5.3 (from 4.3) and PHP 5.6 (from 5.5)
  • [Bug Fix] Storing of attachments with long MIME subtypes (e.g. MS Office formats like docx format with: VND.OPENXMLFORMATS-OFFICEDOCUMENT.WORDPROCESSINGML.DOCUMENT) is supported and will not crash mail retrieving
  • [Bug Fix] Fix issues managing users with apostrophe in their names (like O’Neil)
  • [Bug Fix] Fix issues recording send events for users with apostrophe in their names
  • [Bug Fix] Omit PHP warnings like “DOMDocument::loadHTML(): Tag o:p invalid in Entity”
  • [Bug Fix] Fix issue with timestamps not taking WP timezone settings into account
  • [Bug Fix] A “mail not forwarded” event not being sent out (due to random reasons) will not stop handling of mailing list mails (not cause email loop)
  • [Bug Fix] Failure to open the log file will not crash the process