Emails from our servers sent to Mimecast are being "temporarily rejected" due to greylisting.
Mimecast has docs on this; they say that every time they see a unique IP and sender, they greylist the IP temporarily. They recommend to keep retrying and eventually the IP should get greylisted.
We've configured our Postfix to do this. All bounced emails get retried a few times but Mimecast is not removing us off their greylist.
Our domain has properly configured PTR and SPF records. The IP is also not blacklisted anywhere.
Here is our Postfix configuration:
maximal_queue_lifetime = 1h maximal_backoff_time = 15m minimal_backoff_time = 5m queue_run_delay = 5m
I have also contacted them but I am going to assume they will never reply because we are not Mimecast customers.
How do we go about getting off their greylist?