“553 sorry, that domain isn’t in my list of allowed rcpthosts; no valid cert for gatewaying” problem solving for Outlook, macmail, Plesk 8.2

“553 sorry, that domain isn’t in my list of allowed rcpthosts; no valid cert for gatewaying”
There could be many things leading to the problem. One of them is client inability to authorize to SMTP server. Here’s a quick explanation of what happens and how the problem could be solved.

Several years ago when the Internet was young and all internet users were absolutely honest people the SMTP protocol (the one that works when you’re sending emails) was very simple and quite unprotected. Anyone was allowed to connect to any server, introduce themselves as anyone and send email to anyone in the world. When the Internet expanded beyond those few hundred scientists that used the net of the nets for their fair purposes spam was born. So people realized that they should somehow limit the scope of people allowed to send emails thru given mail server. That means anyone willing to send email using some mail server in the modern world has to authenticate. The 553 error message may mean that your mail client didn’t authorized itself correctly.

There are two basic ways of authentications and dozen of their modifications. The primary methods are

• POP3 lock – the server assumes that anyone authenticated using POP3 is also allowed to send email
• SMTP authorization requires your client to provide login and password before you’re able to send emails

So what you have to do is to enable one method or another on the mail server and configure your mail client. Here are some glitches you might be hit with:

• If you’re using IMAP protocol to retrieve mail from the server you obviously can’t use POP3 lock. SMTP suthorization if your only choice.
• If you enable both POP3 lock and SMTP auth in combination with IMAP mail retrieval macmail client will be able to send email only every other time. I have no good explanation for this

So SMTP authorization looks like you best choice. To configure it in MS Outlook

• Go to Tools->E-mail Accounts
• Select View or Change existing, Click Next
• In the new window select the account you want to configure and click Change
• In the new window click Change
• In the new window select Outgoing Server tab
• Check My outgoing server (STMP) requires authentication, provide login and password if necessary (typically use the same settings as your POP3 account)
• Click Ok
• Click Next
• Click Finish

To configure SMTP authorization in Plesk 8.2

• Click Server in the man Menu
• Click Mail icon
• Check Relaying->Authorization is required->SMTP checkbox. If you or somebody else in your organization use macmail in combination with IMAP uncheck POP3 lock time

Good luck!