OSX Server 10.8.5 email Authentication Issues

I am running email on OSX Server 10.8.5. I am on the same LAN with an email client, the Mail.app from Apple. I had to redo my server for various reasons, and it's giving me all kinds of problems.

I have a user in the server, "house". Login for services only. I'm only running email on this server. So this user's email address is house@mydomain.com as it has been for ages.

On the server:

Full Name: House

Account Name: house

email address: house@mydomain.com

Log in checked

mail stored locally

It's an IMAP account, as are all of them on OSX Server

In my Mail.app:

Account: IMAP

Description: House

Alias: House <house@mydomain.com>

email address: house@mydomain.com

Full Name: House

Incoming Mail Server: 192.168.1.6

user name: house@mydomain.com

password: ••••••••• (yes it is verified)

Outgoing Mail Server (SMTP): mailserver (verified)

TLS Certificate: an Apple cert

Note: I have 4 certs from Apple here, then my Box cert. No clue where that came from, but it expires June 11. In my mail client, I have choice of two of the Apple certs.

My mail server log shows the following:

May 25 13:46:32 mailserver.mydomain.com log[9047]: auth: Error: od(house,192.168.1.4): authentication failed for user=house@mydomain.com, method=DIGEST-MD5

May 25 13:46:38 mailserver.mydomain.com log[9047]: auth: Error: od(house,192.168.1.4): Credentials could not be verified, username or password is invalid.

I have no clue where to even start. I can't log into my own email server. I've checked usernames, full names, account names, passwords, etc.

Any insight appreciated, as to how I can fix this thing. Cheers.