#2145 accepted
Stefan Seiz

Do not store copies in Sent Messages

Reported by Stefan Seiz | October 22nd, 2018 @ 08:14 AM

Is there a preference to disable the storing of copies of sent email in "Sent Messages" on a per Account basis?

Reason is, i have multiple where one of them is an account on an Exchange Server and the Exchange server seemingly also creates a copy in "Sent Messages", so i always end up with Duplicates. And only God knows how to circumvent this on Exchange.


Comments and changes to this ticket

  • benny

    benny October 23rd, 2018 @ 08:50 AM

    • State changed from “new” to “accepted”

    No, such a preference does not currently exist. I do get an increasing number of requests for such a feature because apparently Outlook accounts have recently changed default behavior. Gmail actually has the same behavior, but this is different because Gmail does not allow duplicates in general and therefore it's a bit of a race condition (unpredictable) which copy survives. I believe FastMail also has this behavior.

    Let me first explain the background. Traditionally, IMAP and SMTP are two completely different things. One is used for receiving and storing emails and the other is used for sending emails. There's no (standard) way to connect to an IMAP server and tell it to send message X in mailbox Y. Instead, a separate connection is done with an SMTP server and the entire message is sent to this server. After sending it, the email client uploads the email to the IMAP server in order for the sender to have a copy of the email.

    Today, most often the IMAP and the SMTP server is the same server and therefore it makes sense for SMTP to automatically save a copy in the IMAP account — but it's not standard behavior. More importantly, there is (to my knowledge) no simple way for the email client to know that this happens.

    Now, why has the feature you request not been implemented? It's mainly because it's non-trivial to implement. There's a lot to consider:

    • The two copies are not necessarily identical. For example, Exchange adds a lot of headers. It's also not quite clear what happens when a Bcc header is involved. So, should the server copy or the client copy be the one that survives? Should it be optional?
    • A simple implementation which allows the user to discard the local copy automatically is a risky approach. What if the server reverts its behavior? Then nothing is saved until the user realizes that the setting should be disabled!
    • Also, if the local copy is simply deleted then the sent message is unavailable until the message is re-downloaded from the IMAP server.
    • What if the local message has been tagged/flagged? If the local copy is deleted then this information is lost.
    • If MailMate somehow (e.g., based on Message-ID) never re-downloads the message, but simply “maps” it to its local copy then MailMate is telling the user something that isn't quite true. The two messages are likely not really identical. Gmail, for example, some times rewrites the From header before sending. What is “enough” for MailMate to claim it's the same message?
    • If MailMate does “map” like this then there is a race condition: How long should MailMate wait for the message to appear in Sent Messages before giving up and uploading its own local copy?
    • Most users shouldn't need to know what happens. A solution should work out-of-the-box if possible.

    Based on the above I think a solution could/should be a single Composer setting like this (enabled by default):

    [v] Detect and handle duplicate sent messages

    When enabled:

    • MailMate compares new emails in Sent Messages with recently sent messages. If a match is found then it maps the local copy to the server copy.
    • Preferably, this happens without downloading the entire server copy.
    • Any flags/tags on the local copy must be applied to the server copy.
    • Preferably, it's not a match if important headers are not identical (From, Subject, ...).
    • Preferably, the potential race condition is solved gracefully. For example, the waiting time could be increased/decreased based on whether or not duplicates have been detected in the past.

    I cannot provide a time frame on this issue, but it helps every time I have to reconsider it :)

    Currently, a workaround is to tell MailMate to use a different mailbox for its sent messages. Create it using “Mailbox ▸ New IMAP Mailbox” and use “Mailbox ▸ Mailbox Type” to assign it the “Sent Messages” type. This way you can at least separate the messages and more easily delete one of the sets if needed.

  • Stefan Seiz

    Stefan Seiz October 26th, 2018 @ 06:41 AM

    Hi Benny,

    awesome. Great suggestion.

  • Will Wright

    Will Wright October 30th, 2018 @ 12:29 PM

    I use MailMate with IMAP/SMTP against an Office 365 account, and I noticed recently that my sent messages was full of duplicates :-(

    Apparently SMTP is a protocol used by legacy email clients (their words, not mine!). Here's the blog post which describes the change.

    There's an Office 365 feedback page where you can vote to be able to turn off saving a copy of sent messages which you might like to do if you're affected by this. (Also worth keeping an eye on in case they do add an option to disable this.)

    Here's the link to the original Office 365 feedback page which asked for this feature in the first place.

    I love the workaround - thank you Benny - and the proposed longer term solution.

    I personally can see use cases for the server-side saving of sent messages, but would much prefer it to be optional!

  • Will Wright

    Will Wright October 30th, 2018 @ 12:48 PM

    I also use MailMate with FastMail, which has a Save a copy when sending through 3rd party clients option. If you use MailMate and have that option enabled, then you'll get duplicates in your sent messages.

    Here's a link to the FastMail documentation which explains how to change the setting. There's also a blog post but the interface has changed a bit since that was written.

  • Matthew

    Matthew September 9th, 2019 @ 07:37 PM

    I've got an Office 365 account and I'm also experiencing this.

    Just to confirm that I understand what's going on...

    • The messages are not actually being sent twice
    • They're appearing twice in the 'Sent' folder
    • The reason is that Microsoft is now automatically saving a copy of sent messages, which they did not used to do
    • It's not an issue with Gmail, because they don't allow duplicate messages

    Is that correct? And the workaround is to dump sent messages into a different mailbox? Or just live with 2 copies in the sent folder?


  • Williper Larnloge

    Williper Larnloge October 31st, 2019 @ 08:29 PM

    I'm having the same issue with 365.

  • Klay

    Klay November 27th, 2019 @ 01:02 AM

    Heart broken......this issue has hit me with Office 365 service and the only realistic option is to change my email client....

  • Will Wright

    Will Wright November 27th, 2019 @ 02:20 PM

    I've been using the workaround Benny suggested for over a year (tell MailMate to use a different mailbox/folder for sent messages) and it works fine for me.

    @Matthew - yes, everything you said (except the Gmail not allowing duplicates part, because I'm not familiar with that) matches my experience of what happens.

    @Klay - maybe worth trying the workaround

    Microsoft should really provide a way of disabling this feature.

  • Klay

    Klay November 28th, 2019 @ 01:35 PM

    @Will - now this is where I eat humble pie and admit that I didn't understand the workaround nor did I try it. Having now done so, I can live with it and RELIEVED you posted that response! That workaround is acceptable and more importantly, I can continue to use my most favourite email client. You have no idea how much that made my day.

    Thank you sir.

    @Benny - thank you for the workaround.

  • Jules Bowie

    Jules Bowie December 19th, 2019 @ 07:05 PM

    I experience this also using O365 and accessing via IMAP and smtp. I've done the workaround so I can at least delete these dupes.

  • Colin

    Colin June 28th, 2020 @ 01:56 PM

    I have created a 'sent items' folder and set it as mailbox type sent message as above. Now I have changed to a different smtp server and no longer have duplicates. Now I have the usual sent messages folder and my created sent items both contain all my sent items. I want to remove the folder 'sent items' without losing my sent messages. How do I do this? It seems impossible now to change its type.

  • Shri

    Shri August 13th, 2020 @ 05:12 PM

    Thanks Benny for the informative post on the background and pointing out the complexities in addressing a seemingly simple issue. The proposed workaround is working well for me. Thanks!

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