Emails still arriving to old Exchange server AFTER updating MX Records
First, MX records don't "propagate". They're cached by non-authoritative servers, and fetched from authoritative servers when the TTL expires - none of that involves any sort of "propagation".
This definitely doesn't have anything to do with Outlook.
The servers that are sending to your Exchange server either need their DNS cache flushed, or whomever they are receiving DNS records from needs to do the same. You'll have to figure out who they are and contact them for further troubleshooting.
Really not sure about your whole comment on the Outlook/Exchange and Collegues thing. Sounds like you might have some strange half migrated system setup. This sounds to me like it's misconfigured, but I couldn't say with any certainty without knowing much more about your setup.
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StefanUpdated on September 18, 2022
Stefan 5 months
We have changed our company MX records to point our emails from a MS Exchange server to Google Apps for business. This was done 2 weeks ago, so the MX records should have propagated, which intodns and mxtoolbox confirm.
Since then, around 95% of all emails are being sent to our GMail accounts, and the rest to the old exchange record. Because of this, we have set up both accounts on Microsoft Outlook to ensure that we don't miss out on Client emails.
Could this be an issue with Outlook? When I deleted my old Exchange account from Outlook, I no longer have this problem other than from internal emails from my other colleagues who are using Outlook. But my colleagues using Outlook have trouble receiving emails from clients.
I have tried a DNS Flush on the outlook machines, but that has not fixed the issue.
kralyk almost 10 yearsWhy are Outlook clients still using/connecting to the Exchange server? Is 100% of external to internal email going to the new MX records? You seem to start out the question in one direction (external to internal emails) and then flip to another (internal users still using Exchange).
Patrick James McDougle over 9 yearsI've got the same issue going on. Did you ever figure it out? Was it a misbehaving DNS cache?
Stefan over 9 yearsIt just took a while, things sorted themselves out after a further week or two. Perhaps because of Outlook's DNS caching (as mentioned below) on either our machines OR our clients. Unfortunately, I can't say exactly was did it.