Hello
I am trying to configure SquirrelMail on a XAMPP server.
I have setted up all the imap and smtp settings, it seems working: the login is OK and also the email download but when I try to send an email I get this error:
Message not sent. Server replied:
Requested action not taken: mailbox unavailable
550 5.1.0 Dia81t00F46nFWd01ia8qM authentication failed
I really have no idea how to fix this.
I am trying to do this on a local computer without a domain name, maybe is this the cause? The domain of the email addresses is hosted on another server.
Your message is likely getting rejected as being spam by the mail server of the service you are sending it to; reason being , as you guessed, that you are not sending it from a FQDN.
There is more about this here: http://ask-leo.com/what_does_mailbox_unavailable_mean.html
Try sending a message internally/locally, if that works then this is indeed the cause of the issue.