eM Client won't download from Comcast email servers

I just started using eM Client and I am having trouble downloading messages from the comcast server. What’s odd is that the first time I launch eM Client after restarting my computer the emails download fine. Then after 20 to 40 seconds eM client puts an icon by the email account and says that “An attempt to connect to failed. This could be caused by a temporary server unavailability or incorrect settings …;” I have tried logging directly into my comcast email through their website and it works fine.
When I go to the Account page and perform diagnostics, the IMAP diagnostic says, “Your credentials were rejected.” and the SMTP diagnostic says, “Server not responding.”. But this seems odd given that literally 20 seconds ago it downloaded the email just fine from comcast’s servers. Closing the app and restarting it has no effect.
I have already cleared all the Windows email credentials and triple checked my email account names and passwords.
I am running Windows 10 Pro Version 21H1 (OS Build 19043.1586) and eM Client Version 9.0.1361 (647eeb3). My email server settings for eM Client are as follows:
IMAP - Host: imap.comcast.net
Port: 143
Sec Pol: Force usage of SSL/TLS
Authentication: Use identity credentials
SMTP - Host: smtp.comcast.net
Port: 25
Sec Pol: Use SSL/TLS if available
Authentication: Use identity credentials

I’d appreciate any help you can give me. Also please let me know if my server settings are wrong. When searching for them I found several possibilities. Thanks

Change the IMAP port to 993 and the security policy to Use SSL/TLS on special port (legacy)
Click on Save & Close

Restart eM Client and see if you get the same issue.

Thank you, I appreciate the help. I made the change you asked for and the results are the same.

after 20 to 40 seconds eM client puts an icon by the email account and says that “An attempt to connect to failed. This could be caused by a temporary server unavailability or incorrect settings

As you have already tried a different IMAP Port 993 & Security policy as @Gary advised and your email still only works initially for 20-40 secs and then stops as per your original IMAP Port, and your other mail settings look ok, sounds like either some Comcast mail server issue or possibly an eM Client acct issue, or maybe even something installed locally on the computer interfering with the incoming mail.

So suggest to next contact Comcast support via phone or website and see if any issues their end currently like your experiencing. If they say their end is ok, then backup eM Client via “Menu / Backup” and then remove your Comcast IMAP account and try re-adding it again either via the automatic wizard if Comcast has OAuth or via manual option and see if that fixes the program.

Failing that if you have any eg: Optional Antivirus programs, Optional Firewall / Security programs or VPNS’s etc, completely disable those (to test) and then close and reopen eM Client to see if it then works ok.

Note: Some other Comcast users on this forum had eg: AVG or Avast installed which interfered and disabling those fixed the issues.

Thanks for the assistance. I’ve already been on the phone with comcast for a couple of hours and they insist nothing is wrong on their end. I’ll try your other suggestions and let you know what happens.

The same thing happened to me. I spent all day talking with Comcast. Finally they told me it wasn’t their problem since I could get my email on their website. They told me to contact Microsoft. They did nothing. In frustration, I tried to connect again and it worked. I don’t know what fixed it and if it will stay fixed. Frustrating. It was doing this a few times last week but finally on Friday the entire email program shut down until today.