Duplication of Sent Mail

Some mail services, like Outlook, already automatically copy sent mail to the Sent folder. When Mailspring sends a message, it does the exact same thing, resulting in multiple copies of the message.

This replication gets worse with multiple recipients, including in BCC fields. This half of the problem is related to read receipts. (See BCC'ing many recipients splits the message into one for each recipient · Issue #1669 · Foundry376/Mailspring · GitHub)

However, the message still is only being sent once.

Odd related bug:

I can confirm this bug on Mailspring 1.8.0 and Ubuntu 20.04. For me, this only occurs with Outlook. None of my IMAP accounts have this problem.

It’s useful to note that Evolution had the same problem, which I mitigated by not specifying a Sent Mail folder.

This would be easily resolved with a per-account option for “Copy outgoing messages to send mail”.

The code responsible for moving mail to sent is in Mailspring-Sync/MailSync/TaskProcessor.cpp:1442-1536. I’m going to dig into a bit, and see if I can figure out what’s going wrong, as it is supposed to prevent duplication of sent messages.

Active Task

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I have a problem with Outlook account. When i send a mail i see it two times in my send items folder.
I think the first is generate by office server and the second by the Mailspring client.
Can i have a feature like on other client “don’t save send items” ? I see this problem for other people but never solved :confused:


Can you help me please ?

In thunderbird the fix is To disable saving a copy of sent mails.
I think what is happening is.
You send a message, mailspring puts a copy on Sent folder
Outlook server ALSO places a copy on Sent folder.
Local copy synced to server and Server copy synced to Local
and you end up with 2 sent copies.

So, a fix would be an option to save or not a copy of the sent message.

That was my first thought too, but its quite a bit more complicated than that.

I wish i could help, but my coding skills are very poor :smiley:
I have opened a ticket on nextcloud’s mail app for the same problem and the author changed my tittle from Duplicate Sent messages to Disable storing sent message on IMAP when SMTP server does this automatically. This might give you a hint to whats need to be done!
Me personally i don’t really have much of a problem with this issue, i don’t really send mails i usually receive. But for others might be deal breaker!

Thanks, but I do know where the bug is. See my comments here: Outlook: Duplication of Sent Mail · Issue #2 · Foundry376/Mailspring-Sync · GitHub

It’s just a matter of actually resolving the off-by-one error I describe.

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Just to say I also have this duplication of sent emails and that I am hoping for a fix somehow. I am on Linux Ubuntu.

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Did you think any fix gonna be ready soon ?

@gmarthews @PrincesseLulu Please vote for this issue, and then be patient. This project is entirely volunteer; even the core developer, Ben, does this in addition to a full-time job. If there are updates or a timeline, the thread will be updated. Asking for updates will not speed it up.



Doublons in threads: When answering to a mail it send the mail twice or displays it twice

To Reproduce…

Steps to reproduce the behavior:

  1. Answer to a mail (reply) and send it
  2. When done in the thread it will be displayed twice instead of one



  • OS and Version: Windows 10
  • Mailspring Version: image
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I’m sorry but a volunteer project should not have subscription, but donates. Specially when a product is not ready enough.


Hi everyone

I have the same issue with Windows client and Office 365, so I’ll stop using it because it seems that it will remain open for some time!

I’ll keep going back, greetings

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please vote for the bug resolution

please vote for the bug to be fixed

I’ve voted for this bug to be fixed because I too have encountered this issue. Interestingly enough, it seems that the indicator that the recipient has read the message appears on only one of the copies (presumably the one mailspring itself makes?). Whenever this bug gets fixed, I’d appreciate if the email remaining in my sent folder is the one with that indicator.

I’d like to add, however, that while this primarily effects outlook accounts, I also have an instance of this duplication occurring with an IMAP account – specifically, when I forwarded a few emails from my university account, which is connected through IMAP. The recipient was an outlook account, if that matters, but I thought it worth mentioning in this thread.

Hi everyone , i love mailspring but i have the same issue , i’ve voted for this bug to be fixed.

Hello. This problem seems to still exist. Is there any plan to fix it any time soon? Thank you

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Affects Outlook as others have stated, voted. Hopefully, it’ll get resolved.