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Document ID:	5219
Subject:	What is a dictionary attack
Creation date:	5/31/18 9:55 AM
Last modified on:	7/16/20 11:44 AM

What is a Dictionary Attack?

A Dictionary Attack occurs when someone tries to send emails to addresses that do not have a valid account on your system. There are two reasons for someone to perform a dictionary attack against your server.

• Phishing - Often spammers do not know the actual email address of the recipient. In that case, they try to send messages to a lot of made-up addresses hoping a few will get through.
• Reverse NDR attack - If your SMTP server (either Xeams or a downstream server) is configured to generate NDRs (Non-deliver reports) you can be made a target of reverse NDR attack. Check this page for details.

Preventing Dictionary Attack

Xeams automatically detects a dictionary attack and will block an IP address if too many attempts are made to deliver messages to invalid users. Refer to this page for details.

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