K-9: Can't send email when connected to NordVPN

[yaomtc]

Expected behavior

When connected to a NordVPN server over TCP using their Android client (which I believe is a frontend to OpenVPN for Android), emails should probably send as normal.

Actual behavior

Emails do not leave outbox, but instead I get the "k9 mail errno exception isconnected failed" error.

Environment

K-9 Mail version: 5.403

Android version: 8.1.0

Account type (IMAP, POP3, WebDAV/Exchange): IMAP (SSL/TLS port 493), SMTP (port 465)

[atm1991]

Same issue, Android 8.1 and happens for me on both 5.403 and the 5.503 beta version of the K-9 Mail app. IMAP (SSL/TLS port 993), SMTP (port 465) I can send emails via the webmail or official app of my email host (Zoho) with the VPN on and have no issues.

[8ak5sih222nnb9f6]

Same issue, using OpenVPN for Android 0.7.7. Android 7.1.2
IMAP (STARTTLS port 587). Works as soon as I disconnect from VPN.

K-9 Mail 5.600 (F-Droid)

[jpschewe]

I'm seeing something similar. If I connect using OpenVPN over the cell network, K9 mail works fine. However when I connect using OpenVPN over a wifi network (particularly at hotels), K9 mail times out or gives me the message "AUTHENTICATE PLAIN" on email mailbox rather than refreshing the mailbox. I'm using IMAP with SSL/TLS and SMTP with STARTTLS.

[jpschewe]

I grabbed the logs as specified in https://github.com/k9mail/k-9/wiki/LoggingErrors and found that the problem is the number of connections from my VPN to the mail server. So my report is not due to k9.

[yaomtc]

I don't have NordVPN anymore so I can't test this, so that's fine by me.