Comcast email stops working when VPN changes servers.

Hello, I recently started using Proton VPN for general security. It worked fine with Thunderbird for several months, but recently, Thunderbird has started dropping its connection to Comcast, rendering that email unusable. If I turn off the VPN and reboot without it (or through a US server), it will reconnect, but the moment it switches servers or tries to connect through another country, it kicks out Comcast and won't reconnect until I reboot the computer again. Is there a fix for this? Preferably a way to sign in, and stay signed in, to email only without granting full access to my entire Comcast account? Thank you!