Increase Thundebird's Mass Mailing Capabilities

Martin Brinkmann
Nov 7, 2009
Updated • May 25, 2017
Email, Thunderbird

The desktop email client Thunderbird offers mass mailing capabilities by default. It is possible to add multiple recipients for an email, either to the "to", "cc" or "bcc" fields.

Problems arise however if the number of recipients is extremely large (more than 100 for example) and if individual recipients should not see the other recipients that have received the email as well.

The second problem can be tackled by adding each recipient to the BCC (blind carbon copy) field and a personal email address in the To field.

The first problem can be solved by writing multiple emails whose recipient counts are below the maximum recipient per email limit.

Both solutions increase the workload of the user writing the emails. They also make it difficult to keep track of the process as you now have to handle multiple emails instead of just one.

Last but not least, it is difficult to personalize emails as well, for instance to address each recipient by name.

Mail Merge

Mail Merge is a Thunderbird add-on that increases the email client's mass mailing capabilities. It does so by introducing two new options to the email software: Mass Mail and Personal Mail.

Mass Mail

Mass Mail is ingenious. You start by writing one email that you want to send out to multiple recipients. This includes the email subject, body and attachments.

Then all recipients are added to that email in the appropriate fields. A click on the Mass Mail button (available under File > Mail Merge) will now create individual emails for each email recipient and put them in the outbox of the email client.

Each recipient will therefore get an individual email message so that no other email addresses appear in the mail header.

This process saves you lots of time over the default way of sending out mass emails in Thunderbird.

You can select to send emails right away or save them as draft first. The latter option can be useful to check those emails before sending them out, especially if this is your first try of the add-on.

Personal Mail

One problem of the Mass Mail approach is that the emails cannot address recipients individually.

Adding Hi Frank to a mass mail would send that greeting to all other recipients as well.

That's where Personal Mail comes into play. Personal Mail makes use of variables and csv files to address individuals in mass mailings. Variables can be added to any field in the email in the form {{Variable}}. It is for instance possible to write an email like the following:

To: {{Mail}}
Subject: {{ID}}: Notification
Body: Hi {{Name}}, this email ...

The selection of File > Personal Mail after writing the email will open a dialog with the option to load a csv file that contains the information.

The CSV file uses the following syntax:

The first line lists the available variables, the lines that follow information for recipients separated by a line each.

The extension's profile page on the Mozilla Messaging website offers additional information on variables. It lists for instance variables of address books that you may use in those emails, and detailed step by step instructions on creating these emails.

Closing Words

Mail Merge is compatible with all recent versions of the Mozilla Thunderbird email client. You can download the latest version from the official project website to install it in Thunderbird afterwards.

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  1. JMGG said on January 19, 2012 at 8:25 am

    You said that Outlook isn’t your main email client, so which is your main one?

    1. BalaC said on January 19, 2012 at 9:42 am

      I think its thunderbird

    2. Martin Brinkmann said on January 19, 2012 at 10:15 am

      It is Mozilla Thunderbird.

  2. Salaam said on September 24, 2012 at 9:52 pm

    Awesome! This actually solved my problem… what a stupid bug.

  3. Claud said on December 19, 2012 at 2:08 am

    If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.

    1. Lynda said on February 12, 2013 at 3:37 pm

      THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!

    2. Chad said on November 20, 2018 at 4:24 pm

      Solved my issue! 6 years later and this is still problem…

    3. Ivan X said on January 21, 2021 at 4:50 pm

      Fantastic. Thank you. Size did the trick.

  4. Andrew said on October 26, 2013 at 7:06 am

    This solved my Outlook problem, too. Thank you. :)

  5. Charles said on December 7, 2013 at 7:23 pm

    Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.

  6. garth said on November 7, 2014 at 7:13 pm

    You are a god – thank you!

  7. Faisal said on February 9, 2015 at 10:09 am

    thanks a lot…. work like charm.. :-)

  8. Simon said on March 24, 2015 at 11:36 pm

    Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers

  9. Olu said on April 14, 2015 at 1:35 pm

    Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
    Thank you

  10. Coenig said on July 23, 2015 at 7:36 am

    Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)

  11. Fali said on January 20, 2016 at 4:19 pm

    Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.

    1. MIki said on January 10, 2019 at 11:54 am

      I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!

  12. Christina said on January 20, 2016 at 6:14 pm

    Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007

  13. Oz said on July 22, 2016 at 3:20 pm

    Great tip! Thanks!

  14. Tracy said on September 1, 2016 at 4:48 pm

    Worked for me, too – thank you!!!

  15. shawn said on September 9, 2016 at 10:25 am

    It’s Worked for me, too
    thank you very much!

  16. Jari said on October 31, 2016 at 11:53 am

    I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!

  17. Michel H said on November 30, 2016 at 11:08 pm

    Thank you so much. Solved!
    Considering you published this in 2012, incredible not been debugged by Microsoft.
    Thank you again. M

  18. Ziad Bitar said on January 9, 2017 at 2:00 am

    This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.


  19. Anonymous said on February 15, 2017 at 5:24 pm

    Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.

  20. Rochelle said on March 6, 2017 at 11:59 am

    Thank you, this worked !!!!

  21. anom1234 said on May 20, 2018 at 11:20 pm

    Man, you are a fucking god. Thanks a lot, what an annoying bug!!

  22. JC said on October 12, 2020 at 2:14 pm

    Awesome, this post solved the issue. Many thanks!

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