Every few months my privateemail.com account gets flooded with delivery failures due to a flood of spam emails from my email address. Privateemail uses DKIM keys so I would think its not just a simple matter of spoofing my email. The outgoing emails are all on privateemail servers. I just want to eliminate my computer being the culprit. I use Thunderbird email and am on Zorin Core with Gnome, and everything is up to date. Is there somewhere I could look for any possible trails if something is actually sending the emails from my computer? Thanks!
You can use rkhunter to check for any rootkits:
sudo apt install rkhunter
sudo rkhunter --propupd
sudo rkhunter --checkall
DKIM can help prevent spoofing, but it is not a Proof against it. An adept Spammer can workaround DKIM even if the average spammer cannot.
You could install spamassassin and apply it to Thunderbird:
Maybe check your Thunderbird Add-ons/Extensions for anything unexpected in there.