Symantec 11105111 - SYM MAIL SEC SMTP 5.0 SMS PORT MEDIA CD EN, User Manual

Page: 135 / 170

135 Setting your filtering policy
Preventing relaying
Preventing relaying
You can configure relay restrictions within Symantec Mail Security for SMTP so
that it refuses to deliver email that has a source outside of the organization
(email for which the sender or recipient is not local).
Another way that Symantec Mail Security for SMTP prevents relaying is by
rejecting messages to recipients with addresses that contain specific characters,
such as ! and %.
Configuring external relay restrictions
The following relay options are available:
■
Allow: Relay restrictions are turned off for external hosts. Email from any
remote host can be relayed through Symantec Mail Security for SMTP to
remote hosts.
■
Do not allow, except for listed hosts (one per line): Relay restrictions are
enabled for external hosts. Only email from explicitly named hosts and
domains can be relayed to remote hosts.
Do not allow, except for listed hosts (one per line) is the default.
The source of a message is the computer that contacts Symantec Mail Security
for SMTP, not the From address. The destination is the host portion of the
recipient’s address. If the source or destination is considered local, the Do not
allow setting does not apply.
See “To configure external relay restrictions” on page 136.
A source is considered local if Symantec Mail Security for SMTP is running in
Allow mode or if the host is listed in the Do not allow list, except for listed hosts
list.
A destination is considered local if it is listed in the Local Routing list.
See “Configuring local routing” on page 64.