Having seen a customer of ours migrate to Office 365 recently we also noticed a large delay in receipt of emails from them.
This seems to be related to the Greylisting functionality used in our MailEnable, as the outbound SMTP servers for Microsoft Office 365. However, as there are obviously lots of servers used for this process, it's being delayed by the constant different IP addresses of each outbound SMTP server being different until such time as a single IP address is used more then once.
Now, is there a way we can white-list, for example, all incoming *.outbound.protection.outlook.com connections that, no matter what their sub-domain, so long as they resolve back to an IP address that is correct to that DNS resolution range, would be accepted without further delay?
The reason being there is obviously one or more direct sub-domain mapping for the enterprise as a whole, e.g.:
na01-bn1-obe.outbound.protection.outlook.com
and when you reversed the actual connecting IP back it returns a with a different name to the one it states at time of connection. An example would have been the 207.46.163.189 came back from NSLookup as:
mail-bn1blp0189.outbound.protection.outlook.com
We've seen multiple times where emails come in at the end of the day, but the intended recipient may see the originators correct send time, but that might have been 8-10 hours earlier, so it appears in their mailboxes earlier in the day but just late, so the might not actually see and react to it immediately, or just gives off the impression of bad service. Something, obviously, no one really wants.
Now I know this is something that might also be causing some some concern, but I thought I would ask the question here as many more companies are outsourcing their email to similar such cloud providers (google business etc) how we can handle this without suffering these very long delays.
Kind regards,
Scott
