Unable to set up mail account in 3rd party e-mail software

[Aaron]

When I try to set up my mail account in Thunderbird, it gets suck at trying the password for a little bit, then reports that the credentials are invalid even though I'm using the same password manager to enter them that I use to log into the webmail site, where it works fine.

Has anyone else experienced this problem or has any idea what could be causing it?

[Scott MacDonald]

For the email account username, ensure you've used the full email address ([e-mail]).

[Aaron]

I used my full email address for the username and still received the authentication error.

[Scott MacDonald]

On the computer with your email client, if you PING your mail.domain.ext do you get the same IP address as were you have setup Poste.io?

[Aaron]

Yes, I do.

[Scott MacDonald]

Are you familiar with telnet? Can you attempt access via telnet to POP3 port yo verify connectivity? Basically need to rule out the email client.

As I'm sure you've confirmed the password is correct, proper case, etc..

[SB]

Are you using the correct security protocols? TLS/SSL etc. and has the IP been blacklisted from too many failed connection attempts?

[Aaron]

@CyberMac I'm not familiar with telnet so I'm not sure how to do that.

@shb1 Yes, I'm using TLS/SSL and no, the IP hasn't been blacklisted. I even tried whitelisting it, but that didn't change anything.

[SB]

Tried a different client application?

[Aaron]

@shb1 Yes, same result. Could it have something to do with Poste being behind a reverse proxy? I tried importing the reverse proxy's TLS certificate into Poste, but ran into an error message either because the certificate has the Must Staple extension on it or because it's a wildcard certificate (or maybe both).

[SB]

I have no experience of reverse proxys, see here maybe for some pointers #511

I would try Scott's suggestion of telnet from your client also, this will tell you if its actually accessible externally or not.

[Aaron]

@SB1 Thanks for linking that issue. By switching to "--net=host" and opening the ports in my firewall, I was able to get it working.