Recipient address rejected

[mygeeknc]

I'm trialing PMG and I have two domains setup. I'm watching the realtime logs and I keep seeing a lot of Recipient address rejected: Service is unavailable (try later) messages. Does anyone know what this could be about?

 

[tom]

this is greylisting. check docs for explanations.

 

[GastonZaja]

That's the greylist working.
The first arriving mail will be delayed until the sender server retries sending the email.