Hey! I had the same issue with Gmail proxy over Thunderbird a while back. Turns out, the proxy settings in Thunderbird can be a bit finicky.
Have you tried using a SOCKS5 proxy instead of HTTP? That worked for me. Also, make sure your proxy server supports IMAP/SMTP traffic. Some proxies block those ports by default.
If you're still stuck, check out this guide: [link to a relevant guide]. It helped me a ton!
Have you tried using a SOCKS5 proxy instead of HTTP? That worked for me. Also, make sure your proxy server supports IMAP/SMTP traffic. Some proxies block those ports by default.
If you're still stuck, check out this guide: [link to a relevant guide]. It helped me a ton!