10.6 has introduced the use of Greylisting as a spam prevention mechanism. In short, it denies the first attempt for an MTA to deliver a message, once the server tries a second time (after an acceptable amount of delay, proving it’s not an overeager spammer), it can be added to a temporary approval list so future emails are delivered without a delay.
The problem with this is many popular mail systems, including gmail, don’t exactly behave as expected, so the messages may take hours before they are delivered. To get around this, the people championing greylisting suggest maintaining a whitelist of these popular, but ‘non standard’ mail servers, allowing them to bypass the greylist process entirely and accepting the messages the first time around. The other problem is for companies that send mail through mxlogic and other similar services, the mail is sent from the first available server, potentially causing delayed because they were being sent by a different mxlogic box each time.
The problem with this under 10.6 is there is no gui or interface to inform you that greylisting is enabled (it gets turned on when you enable spam filtering), and so it just takes forever for messages to hit your inbox. You can start managing the whitelist / greylist system, or you can just turn it off:
cp /etc/postfix/main.cf /etc/postfix/main.cf.bak
change line 667 from:
smtpd_recipient_restrictions = permit_sasl_authenticated permit_mynetworks reject_unauth_destination check_policy_service unix:private/policy permit
To the following (removing check_policy_service unix:private/policy):
smtpd_recipient_restrictions = permit_sasl_authenticated permit_mynetworks reject_unauth_destination permit
You can then run postfix with the reload verb to reload the config files, as follows: