Mozilla Thunderbird mail client fails to connect to the Gmail server

This article concerns:

• Kaspersky Internet Security
• Kaspersky Anti-Virus
• Kaspersky Total Security
• Kaspersky Small Office Security

Mozilla Thunderbird may not be able to establish an SSL connection to the Gmail server through the IMAP protocol if a Kaspersky Lab application is installed on the computer and the option Always scan encrypted connections is enabled in it. To the option, go to Settings → Additional → Network → Encrypted connections scanning. 

To connect Mozilla Thunderbird or another mail client with similar issues to the Gmail server, you need to import the Kaspersky Lab product certificate to the mail client manually. The path to the folder where the certificate is located is: C:\ProgramData\Kaspersky Lab\AVPx\Data\Cert\1.cert, where X stands for the version of your application. ProgramData is a hidden folder by default. To access it, enable the displaying of hidden files and folders.

This issue may also occur with other mail clients.

Useful references

How to show hidden files and folders