Problem reported:

I have configured my Account in IMAP with SSL on Port 993 in Thunderbird long time back

Not receiving new mails in Thunderbird


- Mails have suddenly stopped working

- Not able to receive new mails in Thunderbird 

- New mails are visible in webmail

- There is no error popup in Thunderbird


Such a problem is observed in Thunderbird in case there is any change in the  SSL Certificate

Please refer to the following options to address this issue

Option 1: For the latest version of Thunderbird ver. 78.10 and above

Remove the old certificate

- Goto Tools => Options

1. Select Privacy & Security 

2. Click on Manage Certificates under Certificates section

3. Search for all certificates starting with the name COMODO

4.  Select all certificates listed under COMODO

5. Click on Delete and Distrust

6. Click on OK

7. Close Thunderbird

8. Start Thunderbird again

9. New mails should start receiving

Option 2: For the older version of Thunderbird 

- Goto Account Settings

- Disable SSL by changing IMAP port from 993 to 143

- Check if the mails are receiving