HELP WITH DELAYED MESSAGES

[Maggie Mildare]

We just switched from exchange on premises to 365. Now we are having problems receiving into owr accounts ex: user1@mydomain , user2@mydomain , , and this only happens from some domains for incoming mail, ex: usera@myfriendsdomain userb@myfriendsdomain but purchaseorder@myfriendsdomain  (which is a purchase order generated by an automated system). This only happens from some domains : @costco.com.mx , @vepormas.com , @hebmex.com . After a few days, mails enter on their own. I am attaching the header of one of those mails. PLEASE HELP. This has happened since we changed to 365. Important : owr 365 exchange server had the domain name: GPP01.gpp-dist.com and my DNS is gpp-dist.com . I understand this might have been a problem and it was not well configured when we had eschange on it.

[#2]

In the Office 365 admin, setup, domains is it reporting any errors. I'm guessing there's something wrong with the MX records in your dns setup, but thsat admin screen will check them all for you.

[#3]

Nope, nothing wrong with the MX records. Anyway, I am guessing if there was something wrong with the MX records, then I would have problems with all domainsm, not just a couple,. Did you have a chande to look at the header I sent?

[#4]

Has perhaps trying adding the sender IP (148.163.156.53) to the IP allow list in the connection filter settings located in the Exchange Admin Centre -> Protection -> Connection filter ?

It's worth a try.