Knowledgebase: Email Issues
550 Error : Dictionary Attack
Posted by Pacific Host on 04 December 2011 02:50 PM
Dictionary Attack
A method often used by spammers. They send various emails or passwords to a domain hoping that one will succeed. The server detects a dictionary attack when a user attempts to send email to four consecutive invalid email addresses. When this happens the server believes it is getting spammed by someone who is trying a bunch of addresses to see if any of them get through.

Resolution:
The dictionary attack block will be removed after 1 hour if there are no more than 4 erroneous emails in a row. You must stop sending emails and pause your mailing lists. Then wait approximately 1 hour, and it should clear itself. If you were using Outlook, during the wait you can try using webmail to send messages.
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