IMAP connection lost while sending mail

[Paul Kudla (SCOM.CA Internet Services Inc.)]

What version of outlook is your customer using?

and what internet provider (cell, dsl, cable, fiber etc) ?

anything past 2010 can be a crap shoot at best.

I have had many many customers try to use outlook because it is fancier 
interface wise but outlook just does not really support imap properly.

Last time i googled this it cam back with over 2 millions hits on 
outlook imap issues. All suggestions fell back to connect using exchange 
protocol's there was no real answer.

I have been testing myself with 2019 office and it seems to work kinda.

On another major note with outlook it can only handle up to maybe 1000 
emails per folder or it will constantly sync and spend more time doing 
that then anything else.

Outlook also does NOT support idle. (again echange thingy)

I find thunderbird works best (even though they have issues to sort out 
as well here and there)

I run thunderbird and can comfortably run up to 10000 emails in a folder.

It's a microsoft thing pushing exchange / outlook 365 against imap.

This is NO Fault of Dovecot / Cyrus or any other imap server.

Best suggestions for outlook look is to use

Port 143 for imap (you can use ssl on port 143)

Port 587 for smtp (25 is sometimes blocked by your isp) - Note on smtp 
connections there are some isp's blocking normal ports, i had to open up 
10000 on my postfix to get around at&t blocking smtp sends from a 
tethered cell phone connection for one of my customers which fixed the 
issue.

Also outlook timeouts for both send and receive should be pushed up to a 
couple of minutes to cover any timing issues (although 30 seconds should 
be ok in most cases i have found outlook to fail with unknown reasons).

One more thing about outlook is to speed up the user interface in some 
cases they will give you an option on the bottom of the inbox to load 
more messages, this should be checked as i have had several customers 
forget about old emails and the inbox could just simply be going past 
1000 messages without any kind of warning. (see above)

Hope this helps






Happy Friday !!!
Thanks - paul

Paul Kudla


Scom.ca Internet Services <http://www.scom.ca>
004-1009 Byron Street South
Whitby, Ontario - Canada
L1N 4S3

Toronto 416.642.7266
Main 1.866.411.7266
Fax 1.888.892.7266

On 5/6/2022 3:53 AM, Philipp Ewald wrote:
> Hello,
> 
> we have a strange problem.
> 
> Costumer use Outlook to connect to our IMAP and SMTP Server.
> While sending Mails Outlooks reports connection lost. In Mail log there 
> is no reason logged or something else.
> 
> What i dont understand is that IMAP lose connetion while using SMTP. 
> Outlloks reports problem by moving mails into Send dir.
> 
> Is that a Outlook problem?
> 
> i have enables debug logging and cant see any reason :(
> 
> Network was already testet.
> 
> 
> any ideas?
> 
> Kind regards
> Philipp
>