Turns out that this issue doesn't appear to be caused by the self-signed certs! There is a new thread, "GNUMail - Messages with HTML body", where I believe the main issue may be.
I'd like to document some of my findings here in case someone stumbles upon this thread in the future. While testing this with Thunderbird, I found out that GNUMail wasn't behaving so oddly because of the self-signed cert. If that was the issue, Bridge would have thrown this error (which occurred when initially connecting from Thunderbird): ``` ERRO[May 16 08:27:45.779] Cannot upgrade connection error="remote error: tls: bad certificate" pkg=gluon/session session=16 ``` However, GNUMail still behaves oddly with ProtonMail: When trying to list mailboxes to limit the subscriptions, it doesn't work initially. As a workaround: 1. Go to Receive options -> List 2. Send -> SMTP mechanism -> Check supported Any time the account settings were opened, this workaround had to be used. Sometimes, there would be a SEGFAULT when trying to change which folders are subscribed to. The only way to get IMAP to connect after a restart is to go through the SMTP workaround above and then Receive options -> Check supported. Regardless, messages that aren't plain text fail to load. -- Luke Lollard On Wed, Apr 23, 2025 at 10:38:56PM +0000, Luke Lollard wrote: > Howdy, > > During the last meeting I mentioned that I couldn't get GNUMail working > while testing it with Gmail and [ProtonMail Bridge][1]. I went back and > tested it some more, and I can get Gmail working by setting the secure > connection to SSL (though it won't list which folders to sync). > > I still can't get Proton Bridge to work though. What may be causing the > issue with Bridge is that it uses a self-signed cert. With Mutt, I can > use `set ssl_verify_host = no` to get it to work. Proton shows that in > [Thunderbird][2], the user can confirm a security exception for this > when setting up the connection to the server. > > Is there some way to use this with GNUMail? As much as I love Mutt, I'd > like to try out my email with a GNUstep app. > > > [1]: https://github.com/ProtonMail/proton-bridge > [2]: https://proton.me/support/protonmail-bridge-clients-windows-thunderbird > > > --Luke Lollard
