Wolfgang Breyha via Info wrote on 16/01/2026 16:25:
I see a lot of Outlook 2024 clients (eg. imap id "version"
"16.0.19426.20218","16.0.19530.20074",...) in my logs which enter an
infinite "append/expunge" loop for the same message. Only stopped by ending
Outlook or the frontend process of cyrus.
Some more details I found so far:
*) Outlook loops between two versions of the same Mail
*) one with reordered X-Cyrus-Session-Id: and Received: headers.
Yes, it indeed reorders Received: Headers *sigh*
*) one with original header order
*) each new append gets brand new MIME-boundaries... which prevents cyrus from
detecting guid duplicates.
The exact steps IMAP wise (from cyrus session logs) are:
*) append a new copy resulting in UID "n"
*) enter idle
*) immediately leave idle again
*) noop
*) set delete flag on n-1 copy
*) idle+noop again
*) expunge the n-1 copy
*) idle
*) UID FETCH n+1:4294967295 (UID FLAGS RFC822.SIZE BODY.PEEK[] INTERNALDATE)
*) IDLE ... DONE after 1-7 (maybe more?, but not seen so far) seconds
*) ... loop
detected Outlook Versions are
16.0.19029.20156
16.0.19426.20218
16.0.19530.20074
.. and older Versions of 16.0.19* as far as our logs reach.
So, I'm assuming that everybody with a large enough user base, cyrus "delayed
delete" and those Outlook Versions as Clients should see this in his auditlogs
and spools regularily. I see about 1-10 userids per day for ~100k user base.
Greetings,
Wolfgang
--
Wolfgang Breyha <[email protected]> | https://www.blafasel.at/
Vienna University Computer Center | Austria
------------------------------------------
Cyrus: Info
Permalink:
https://cyrus.topicbox.com/groups/info/T1643a70fc002bdcf-M7e453b99e5f6d0f57e2c2062
Delivery options: https://cyrus.topicbox.com/groups/info/subscription
