IMAP failing in outlook

Corcent used Ask the Experts™
A client of our's email isn't working via outlook. I thought perhaps the pst was bad, but it is failing on all computers with outlook. I tested on their system to the web version and it signed in fine. I went back and deleted the mail account on their computer and set it up as active sync and it works fine from outlook. However, if I try to add their email as an IMAP as it is created on the mail server, it fails.

I adjusted the IP from 143 to also try 993. Also attempted with the firewall disabled. It was working fine for a while up to today. The error is uploaded.
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Brian BEE Topic Advisor, Independant Technology Professional
IF it was working and now is not, the issue is probably not the computer. Perhaps the network firewall is causing an issue? Might be worth someone looking at the logs to see if traffic is being blocked.
If it was working fine till today, it could also be the server that has either temporary IMAP problems, or has shut down IMAP as an option altogether.
But you didn't upload the exact error, so it's still just a guess.

You can double check by just adding the account to your smartphone. If it also doesn't work, call the mail provider.
David FavorFractional CTO
Distinguished Expert 2018

Best option for testing IMAP is always use telnet (insecure) or openssl (secure).

Trying to debug IMAP problems with GUI clients is near impossible.

First test will be to determine exactly what services are running on your host/IP using...

sudo nmap -F host-or-IP

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This will tell you IMAP ports which are active.


Thanks for the help. The issue ended up being that there was too many failed attempts and the IDS system had blocked them from signing in.

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