358
Timeout of unused entries
This parameter determines how long SX-GATE will accept an initial retransmission.
If none occurs, the combination of source IP, sender and recipient will become
unrecognized again. A low value will help to keep the internal database small and it will
also reduce the risk that a connection is considered to be a retransmission by mistake.
On the other hand delivery of requested emails might fail.
Relay servers which retry delivery after longer periods of time
will not be able to deliver emails to SX-GATE if the chosen value
is too low.
Timeout after last use
After a retransmission, the corresponding combination of source IP, sender and
recipient will be stored in the automatic whitelist. The whitelisting will expire after the
period of time determined by this parameter. However each new email will reset this
timer.
Sender whitelist
This list will accept IP addresses and DNS names of mail servers. The greylist module
will always accept emails if the connection's source IP is whitelisted. It is also possible
to insert email addresses of individual senders or a complete email domain. To whitelist
all the emails from the "example.com" domain, please enter "*@example.com".
Keep in mind that the sender address of an email can be faked
easily. Greylisting will check the envelope address only.
Recipient whitelist
To make sure that certain recipients will never be delayed, you can add the
corresponding addresses here. To disable greylisting for a whole domain, use an
asterisk (e.g. "*@example.com").
14.5.3-C
SPF filter
SPF is the acronym for "Sender Policy Framework". The owner of a domain can publish
a DNS record indicating that only specific servers are permitted to send emails for
the domain, i.e. all emails from this domain have to be sent or relayed through these
servers. The recipient can lookup the SPF details in DNS and reject non-compliant
emails. Both, the HELO name and the envelope sender is checked. The HELO name
is the hostname used by the sending system to introduce itself. The envelope sender
is the sender address used by the SMTP protocol and does not have to be the same