Q:

E-mails consistently delayed

My application is configured to send out email notifications when an event happens. Sometimes this is fairly often (every minute), and every email has an attachment (up to 6-10 attachments), so each email can be pretty hefty, but not ridiculously so (500k per email is the maximum we would ever reach).
The problem we run into is that the emails will get delayed. They will still be delivered, but there will be a delay in there. The strange part about the delay is that it is very consistent (e.g. all emails arrive 1 hour late).
I thought this was a problem with my email server, so I moved my mail service to a (paid) virtual server with lots of memory, but that didnt seem to help (and I have plenty of resources left).
Does anyone have any insights into what might be factors here, or what kind of options do I have? Is moving to a paid SMTP service likely to solve this problem?
Thank you,

A:

You need to look at the SMTP headers to see where the delay is.
Once you know where the delay is, you know who has control over that delay, and it may not be you.

A:

The delay may be related to greylisting occurring at the receiving server(s). I agree with Hutch: you need to find out where the delay is happening. If the receiving servers have implemented greylisting as an antispam measure, it may be possible to whitelist your emails so they get accepted immediately.

