Librem One SMTP recently hangs with ProtonVPN on

Since ProtonVPN ‘help’ desk only advise me to keep trying an unspecified number of US and ex-US servers, I’m posting this here in case it is better known to Librem One users.

In the last few weeks, SMTP hangs when ProtonVPN is connected. As soon as I disconnect ProtonVPN, I can send the mail. This is a new problem, and I have made no changes to the default configuration I get from Thunderbird. Receiving mail is unaffected.

Advice on troubleshooting also appreciated. Are there logs could I inspect?

With the VPN connected does all SMTP hang or only SMTP to the Librem One SMTP server?

Refer item 16 for enabling SMTP logging in Thunderbird.

Any chance that the VPN is blocking port 25 outbound? What port are you attempting to use for SMTP anyway?

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Thanks for tip on Thunderbird logging, and also reminder (oops!) to check my several SMTP servers.
As it stands, the issue affects a SMTP server as well, so not a Librem One issue.
Nor is it port-specific.
Accordingly, will mark your reply as Solution.

Almost all non-enterprise connections block outbound from the customer port 25 to help with spam. I’m surprised you were on a connection that was allowing it to work in the first place :slight_smile: Always configure your mail clients for sending smtp on port 465 or 587 depending on what your server supports.

To be clear, neither of my SMTP servers was using port 25.
They are set up to use 587 + STARTTLS and 465 + SSL/TLS.

ahh perfect ok, so it was just the protocol itself! Carry on… :slight_smile:

Not if you use a VPN …

Hmmm. OK. I didn’t see an actual solution there. It suggests that the problem is not with the SMTP server though.

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Exactly. It’s a ‘solution’ at least inasmuch as it excludes any Librem-specific issue.
I expect these logs will help me debug, and maybe elicit better help from Proton.

OK. My starting point would be to determine whether the TCP connect fails or whether the TCP connect succeeds but the SMTP session fails later on.