Roundcube Webmail

I have an extremely frustrating situation with Roundcube Webmail:

A client of mine has asked for a WordPress server and a full service email system. The email system is registered already, and working in Thunderbird with the following settings.

Redacted Thunderbird settings

But it just WILL NOT work with Roundcube. IMAP works perfectly, but it won't send messages due to SMTP error 535. Here's the settings I've tried:

$config['smtp_server'] = 'ssl://mail.dynu.com';
$config['smtp_port'] = 465;
$config['smtp_user'] = '%u';
$config['smtp_pass'] = '%p';
$config['smtp_auth_type'] = 'LOGIN'; # PLAIN returns error 504
$config['identities_level'] = 3;
$config['language'] = 'en_GB';
$config['mime_param_folding'] = 1;

The database and des_key settings are there as well but I didn't include them as they contain private info. I've tried some of the common fixes like changing SMTP user or password to blank, which caused other errors.

This happens with 1.4.3 and 1.2.9, and I can't find a fix. I've been at this for days and it just won't work. But I know this isn't an email account problem as mobile apps work, Thunderbird works and (as stated) IMAP works in Roundcube, only SMTP doesn't.

I'm not going to copy/paste the log as it contains the password, but the problem seems to be with the password. I have checked the password REPEATEDLY and it is 100% correct, no doubt about that (plus IMAP wouldn't work if the password was wrong). It just keeps being rejected, as if Roundcube is sending the wrong password somehow. One note, [12] is at the end of the send password line in the log, if that's the char count, that would explain it as the password is 9 chars long.

I don't know what to do about this, and I'm not willing to install Squirrelmail for a client as it doesn't seem to be maintained anymore. Any help would be much appreciated.

EDIT 1; Fixed a formatting problem where the smtp_server setting wasn't showed.

EDIT 2; I reset the database and config files and re-ran the installer with the most basic settings. No plugins, no SSL, just URL's and passwords. Without SSL, SMTP works fine, but with it, error 535 seems to persist. This is not ideal as my client is going to use this email system with WordPress, so passwords (although temporary) can be sent via these emails. As far as my research tells me, error 535 means 'incorrect auth data'. Why does simply using SSL change this?

Solution 1:

Turns out I'm an idiot, I was using mail.dynu.com when I needed to use smtp.dynu.com. My apologies for wasting your time.