Thunderbird Alternative Opera Mail

Martin Brinkmann
Jul 8, 2012
Updated • Jul 8, 2012
Email, Thunderbird

Having used Thunderbird for several years I was quite disappointed by Mozilla's announcement to move development priorities to other projects. While that does not mean that Thunderbird will be discontinued anytime soon, it means that the email client will only receive stability and security updates from Mozilla, and -maybe- improvements or additional features from members of the community.

It is still a perfectly fine email client for many users, and that is not really going to change in the near future. Having said that, Mozilla's priority switch gives me an opportunity to look at other desktop email clients to see if they are good Thunderbird alternatives.

Today I'd like to start with Opera Mail. I have actually used Opera Mail before I started Thunderbird. The focus will be on key elements that are important to Thunderbird users:

  • Is it possible to import emails, accounts, contacts and the like
  • Are there core differences between the clients
  • Issues

Importing Thunderbird accounts and data

This is without doubt one of the most important factors. Who would want to switch to a desktop email client that can't import old emails, the accounts or addresses?

Thankfully, Opera Mail supports importing that data from Thunderbird. The process itself on the other hand is not really that straightforward, as you can only import one account at a time. If you have configured ten or so email accounts in Thunderbird, you'd have to process them all one by one. An option to import everything at once is missing.

To start, click on the Opera button at the top and select Mail and Chat accounts from the context menu. Here you click on Add > Import email > Import from Thunderbird.

import from thunderbird

On the following screen, you need to click on browse and select the Thunderbird prefs.js file that is found in the Thunderbird profile folder. This is usually located in C:\Users\username\AppData\Roaming\Thunderbird\Profiles\random.default.

opera mail thunderbird import

Importing may take a few minutes depending on the number of emails that are stored in each mail folder. It took about three or four minutes to import about 20,000 emails from one account.

Opera will import all messages from the selected mail folder but not the underlying folder structure which can be an issue for Thunderbird users who have organized their emails into folders.

Contacts were not imported by default, and Opera itself only seems to support importing Opera Address Book files. To import your Thunderbird contacts into Opera you need to first export the address book in Thunderbird, then convert it into Opera's format, before you can import it into the mail client.

In Thunderbird, click on Tools > Address Book. In the address book listing, select Tools > Export, and select comma separated in the save dialog. You can use this web service to convert the comma separated listing into a format that is supported by Opera. Once done, select Opera > Settings > Import and Export > Import Opera Contacts, and select the address book file from your local directory.

There are a few things that you need to make sure of before you start importing messages:

  1. Make sure all messages are downloaded to Thunderbird completely. If you are using a setting where only the header is downloaded, only that header information will be imported into Opera.
  2. If you do not want deleted messages to be imported into Opera, compact the mail folders before you start the import. This is done with a click on File > Compact Folders.


Once you have imported your first account you will notice several differences right away. Opera displays a unified mailbox at the very top where messages from all accounts are listed in.  The email sidebar furthermore lists mailing lists that you are subscribed to or are receiving messages from, labels, attachments sorted by type, and after that inbox and sent folders for all accounts individually.

Especially the attachments listing and the unified inbox need to be mentioned here as it may speed up access to attachments that you receive.

opera mail

One interesting feature is the ability to filter the display by mail account. For that you right-click on a blank spot in Opera Mail, e.g. in the sidebar, and select the mail account that you want to display messages from.

Just like Thunderbird does, Opera Mail blocks remote images from being displayed right away, with options to whitelist accounts so that images are displayed all the time.


I have experienced a few issues in Opera Mail that I have listed below:

  • I had about 60k emails in the unified folder listed, and it took some time to sort the mails in the folder. Switching to it sometimes too took a second or two before the contents were displayed.
  • I could not figure out how to import my folder structure into Opera Mail. If there is a way, I did not find it.
  • Both trash and spam were not shown in the unified folders nor in the individual mail account folders. While I have not verified it, it almost seemed as if trash and spam contents were displayed in the unified folder just like regular mails were.
  • Contacts were not imported automatically, requires conversion to work at all
  • There is obviously no option to import Thunderbird extensions into Opera

The two biggest issues for me are that the import is not importing everything at once, including all address books and mail accounts, and that you may run into performance issues if your mailbox exceeds a certain number of mails.

Closing Words

You can overcome the performance issue if you backup and delete mails that you no longer need to have access to at all the time using a program like Mailstore Home, but that is not an optimal solution. Having said that, Opera Mail offers several interesting options and features to its users, like the previously mentioned attachment filters or the ability to filter by individual mail accounts.


Tutorials & Tips

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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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