Emails being routed to old mailboxes, three weeks after changing MX records

Question

We have moved our email hosting from our old hosting provider to Office 365; however, we still use the old provider for website hosting... so it is imperative that we receive the invoices from our old hosting company in our new (i.e. Office 365) mailboxes.

I changed our MX records three weeks ago to point to Office 365 and was just about to go back to delete the old mailboxes to free up space (for our website) but noticed that our billing notifications from our old service provider are still going to the old mailboxes, which we no longer check.

It doesn't look like a DNS replication issue as it has been nearly a month now. It seems to me that the original hosting company's mail servers are simply not checking our MX records as they still think the account is hosted by them.

If I log in to our old webmail system and email one of our email accounts, the email goes to the corresponding mailbox in the old system, rather than to Office 365. If I delete one of our old mailboxes then attempt to send an email from old webmail system to the deleted mailbox, there is a delivery failure "I'm afraid I wasn't able to deliver your message to the following addresses. This is a permanent error; I've given up. Sorry it didn't work out." error.

The billing notifications we receive are from "billing@(OldHostingProvider).com", most likely managed by the same mail server as our old mailboxes used to be on.

Is it normal to see emails sent from an old mailbox not go to the mailbox on the new system, and what would be the best way to ensure our billing notifications go to our new mailboxes in future?

Answer 1

Most probably, you'll only have problems with mails from your old provider (and any other hosts on the same "shared hosting" system)

This is because you didn't inform your old provider that you're moving your MX (and you should have), so in their local configuration they're still configured as authorative for your domain. So, any mail originating from that system will just "know" they need to deliver mails locally on oldprovider mail server, instead of routing them out to the internet.

Which happens to be wrong, because you made an error of not informing them.

So what you need to do is contact your oldprovider, and tell them you will continue using their web services, but that you have moved mail elsewhere, so they need to remove mail configuration for your domain.

After that, their mail servers will consider your domain as external (same as any other one not being their customer), and will route it out to the net, where it will reach your new hosts.