Plesk Error Massage 553: “Message did not Reach Intended Recipients. That Domain isn’t in my list of Allowed RCPThosts”.

Problem:

When send an email, you get this error:

“Your message did not reach some or all of the intended recipients. 553 sorry, that domain isn’t in my list of allowed rcpthosts.”

Solution:

1. Log in as administrator to the Plesk control panel.
2. In the Server Administration (click “Server” in the menu)then choose the “Mail” icon.
3. Select the tab “Maximum letter size and relay mode parameters”.
4. Check the box “POP 3 lock time”.
5. Click “Set”.
6. Restart “PSA”.

Edit:

Alternatively, you can check out Swsoft's knowledgebase entry regarding this matter:

http://kb.parallels.com/en/168
Source: mohammednv