Posting the complete error message is sometimes useful. Is that your IP address?

Sorry to hear about your issue, but it has nothing to do with Thunderbird. You can use the following to check on IP address and follow any instructions to get yourself taken off the spam listing. I first tried spamhouse : * https://check.spamhaus.org/ and got: ''The machine using this IP is infected with malware that is emitting spam, or is sharing a connection with an infected device.'' ''As a result, this IP is listed in the eXploits Blocklist (XBL) and the CSS Blocklist (CSS)'' ''Click on Show Details to see if you can request a delisting from this blocklist. This will also display any further information we have relating to this listing.'' You can also check IP address here: https://mxtoolbox.com/blacklists.aspx Additional info: https://iplocation.io/ip-whois-lookup/119.12.208.149