XnetSolutions SX-GATE, Руководство пользователя

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14.5.3 SPAM/Virus/Malware 352
This feature may also affect regular emails.
Check HELO/EHLO
This option enables a sanity check on the hostname part of the welcome message,
presented by the sending system. The hostname must include at least one dot and
may not be equal to SX-GATE's hostname. Otherwise the mail will be rejected.
This check is not performed for authenticated connections and
connections from IPs listed below "Local IP addresses" in menu
"Modules > Mail Server > SMTP settings" on tab "Relay control".
Also emails retrieved from a POP server are not affected.
Check reverse DNS
Enable this option to test the DNS information provided for the source IPs of incoming
connections. Often home PCs are abused for SPAM delivery. Many of these fail to pass
the reverse DNS check.
Neither authenticated nor local connections will be affected by
this check. Mails retrieved from a POP3 server won't be tested
either.
for existance
Select this mode to reject emails if no reverse DNS entry exists.
forward confirmed
A reverse DNS entry must exist here, too, but in addition it must be forward-
confirmed. That is, the hostname returned from the reverse lookup is resolved
back to an IP by an other DNS query. If this IP differs from the original IP, the
mail is rejected.
This feature sets high expectations in terms of DNS
configuration. Regular emails may be affected in individual
cases.
Check sender domain
With this option you activate a verification of the domain part of the sender address
for each incoming mail.