K-9 Mail client strange behavior?

[wtherrell]

My K-9 Mail client sends mail OK when I am on my WiFi network. But when on 4G or 3G I consistently get a notice that some mail failed to send. Notice in pull down shade is truncated to "530: Authentication is..." And can't read the rest. Messages in outbox simply will not send until I switch back to WiFi. Does anyone know what they notification message is actually saying or how I can find out. I suspect that the mail server trusts incoming messages from my home network since that is where my main PC Outlook Account is based. When I go into sending mail Outgoing Server settings and click next the settings seem to verify that no sign in is necessary. When I try to enable authentication, I have tried all the possible combinations of authentication types but all of these fail to verify the outgoing server. Port with no sign in required is 587--works with WiFi but not 4g or 3g. Should I be using a different port for authentication purposes. Has me stumped at this point. Gmail seems to work OK but that is set up to my Pop3 through gmail site and has been for a long time, so I would expect it to work. Lot's to like about K-9 but this will cause me to uninstall it if I cannot find a solution. Anyone else run into this?