ZCS Administrator Guide 8.0
ZCS Administrator Guide 8.0
Open Source Edition

Zimbra Mail Transfer Agent > SMTP Restrictions

SMTP Restrictions
You can enable restrictions so that messages are not accepted by Postfix when non-standard or other disapproved behavior is exhibited by an incoming SMTP client. These restrictions provide some protection against spam senders. By default, clients that do not greet with a fully qualified domain name are restricted. DNS based restrictions are also available.
Important: Understand the implications of these restrictions before you implement them. You might have to compromise on these checks to accommodate people outside of your system who have poorly implemented mail systems.
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