Hi haran. There are several posts on this. Search in Community on thunderbird and tls. One user came up with the suggestion below. If you try it, you might then be able to use the secure options in Thunderbird. It won't be as secure as TLSv1.2 but will still be encrypted.   I had a similar problem a few weeks ago starting 23 July. I couldn't send or receive email using Thunderbird. I finally figured out that TPG had downgraded their version of TLS   The solution was to go into Thunderbird Configuration and set the parameter security.tls.version.min down from 3 to 1. It all works now!   ... View more