On 27/10/2024 09:40, Scott Q. via mailop wrote:
Has anyone else noticed that Outlook doesn't seem to make use of (UID) COPY commands in IMAP ? When you copy/move messages it downloads them and appends them instead which makes the entire process quite slow. Usually when it does that it also seems to re-arrange the headers.

Yes, we have noticed this. It's a stupid decision. It's 20-30 bytes of data transfer to copy a message using IMAP, it's potentially MB of data to download and then APPEND.

Not only that, but our server uses links to copy a message, so if a 'COPY' command is sent, it takes up a few more bytes on the server disk for each copy of the message. With the download/APPEND method it has to store the whole new message again. Even if it did a hash on the message contents and searched for duplicates that way, that's work that should be unnecessary, and, as you say, there's no guarantee the uploaded message will be byte-for-byte exactly what the downloaded message was.

(A slightly-related thing we have seen is that occasionally, Outlook will go, for want of a better word, 'loopy' (pun intended). It will download and APPEND the message, and then delete it, and start again, and do this repeatedly - many times a minute. The server responds quickly, and with an OK response, and Outlook logs no errors, just does it. The user is often unaware of this, but we have seen cases where it has APPENDED and then deleted the same message >1000 times before someone spotted it. This adds quite a lot of load to the server because of the APPEND rather than COPY, and also, if the server is doing any sort of message auditing/archiving, those 1000+ copies of the same message can really use up hard disk space...)

Are there any reasons why it might be beneficial to do it this way ?

None at all



Paul
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