Probably not just thunderbird but any email or similar app.

I had Thunderbird running in email mode.

I started a VPN to access a newsgroup site that seemed to be blocking me.

I made my benign post then noticed that all my email accounts had
messages from GMAIL and MS that my email was under attack.

Well it was just that Thunderbird was checking my email accounts with a
very different IP address.

So I am having to go to each account and tell them it was me.

Remembering next time to shut off any email app while on the VPN.

And now on the radio there are folks pushing Norton VPN etc and what
chaos that will cause for email accounts.