Greylisting is NOT enabled on your domain unless you request it.

When we first implemented greylisting it reduced spam by 80-90%! 

All authentic mail servers will try and resend messages that do not do through on the first try.  For example your server hosted here will attempt to resend messages every 15 minutes for four days before giving up.

Spamming servers send out millions of email messages each day.  Their servers cannot be burdened with resending messages that do not go through on the first try.  Since spam messages do not carry vital information, if they do not go through on the first try, the spammer’s server will just discard the message.

Greylisting works by exploiting this information.  If greylisting is in effect for your domain, then ALL received messages are rejected on the FIRST try.  Since a spamming server cannot waste time resending a message more than once you will never get the SPAM email. 

If the sending server resends the message more than 15 minutes after the first attempt then the message is accepted and the sender is added to a “whitelist” for 8 weeks. 

The DISADVANTAGE to greylisting is that whenever someone sends you an email for the first time it will be delayed for at least 15 minutes.  As long as they send you an email at least once every 8 weeks, all subsequent emails will be delivered immediately.