XnetSolutions SX-GATE, Руководство пользователя

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14.5.2 SMTP settings 344
Block unencrypted mails sent to mail address and domains
Email to recipients listed here must always be encrypted. You can enter individual
recipient addresses or complete mail domains (e.g. "user@example.com" or
"example.com").
14.5.2-D Relay control
It is crucial that only internal IP addresses are allowed to send mails to the Internet,
unless authorized by e.g. authentication. Otherwise SX-GATE will likely be abused as
an "open relay server" by SPAM mail senders.
Independent of the source IP it is always possible to send
emails to addresses within the local recipient domains. This
includes both, domains delivered to SX-GATE mailboxes and
domains forwarded to specific (internal) mails servers. Also
Authentication is never required in these cases.
Local IP addresses
With this control you can define which IP addresses are considered to be "local". Unless
restricted by other options, only the addresses included here will be able to relay mails
to the Internet offhand.
You should never grant this right to any IP.
You can also use this feature to allow Internet mails only for
some systems while all others may only send internal mails.
Here, the IP address of the system which sends the mail to
SX-GATE is decisive. The following options allow you to allow
Internet mail per user.
SMTP-Auth required for local users
If this switch is active, SX-GATE will not relay emails to the Internet, if the mail was sent
from a local IP address without authentication. Local IP addresses are those listed at
"Local IP addresses" above.
Use this feature to allow the delivery of emails to the Internet only for specific
local users. You can give the SMTP-Auth privilege to groups at "System > User
administration > Groups".