My email is on my private servers and I have an OpenVPN tunnel for k9mail on our Android phones.
When using OpenVPN I am able to send from k9mail whether connected through cellular network or wifi. However when on cellular network I am usually unable to fetch mail - I can only reliably fetch mail when on wifi. This is all the more annoying because occasionally it does fetch when on cellular, nost not reliably.
OpenVPN is making the tunnel whether on cellular network or wifi. My outgoing server is Postfix and my imap server is Dovecot, both those and my OpenVPN endpoint are running on Gentoo Linux.
I thought I had some setting wrong on the phone, but I validated that k9mail had full access to data even when Data Saver was active.
I had a problem with the same symptoms while in Yellowknife. It turned out I was at the edge of the cell towers range. when I was in the back of the house it would not work properly. I had to be in the front of the house. It also had to be decent weather.
This also caused delays with sending/receiving texts.
I wound up just keeping my phone on the wireless LAN for email… had to just deal with the texts.
No error, the little indicator keeps spinning and spinning, and at some point I have to get back to the real world.
To put it more simply, when I’m at home and the phone is on my LAN and desk, an email will show up on Thunderbird and within a minute the phone will give a notification sound. (Is this “push”? (or poll)) Same thing when I’m on wifi. And once in a blue moon on cell. I normally don’t have to tell it to fetch, it usually just shows up.
If there is a logfile and you can point me to it I can take a look.
OpenVPN says it has established a connection, and I have the little key up in the status area. Outgoing mail works just fine also, as sent by k9mail to the postfix server in my basement. I’m in the cellular backwater of Vermont, so I don’t always have enough signal at home to test this and have to go somewhere. My normal test consists of two emails, one from my gmail address to my home servers and the other from k9mail to my gmail address. From what I’ve seen, this latter path works reliably.
This is the first I’ve heard of TURN, I’ll start looking it up, and if you have a reference I’d be interested in seeing it.