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Email bounce backs

Posted on 2014-11-14
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Last Modified: 2014-11-24
Hi all,

We recently migrated to Office 365. Using Mimecast as a failover. We hit problems with DNS when 123-Reg MX record dropped. Re-instated the MX record but still getting random bounce backs from clients. Deleted cached email addresses but still getting host not found. Suspect that it is a local DNS issue. WHat is the standard TTL on DNS records for MX records.

Thanks
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Question by:ncomper
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Andy M earned 500 total points
ID: 40442418
DNS records can typically take anything from 24-48 hours to update so if the MX record was lost you may need to wait upto 2 days for it to propagate to external sending systems.

This said I've seen some domain hosts set so the records have a TTL of 1 week!

If you go to network-tools.com, punch in your domain and look at the dns records you can see the expiry set on the SOA record which will give you an idea of the TTL.

Are the bouncebacks happening when you send an email to a third party or when they send to you? What does the bounceback say?

If the emails were working fine before the MX records went and nothing has changed since aside from the MX been reinstated it sounds like it's just dns records waiting to update.
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by:ncomper
ID: 40461647
Thanks for the feedback  it was a mixture of replication AND legacy MX records that should not have been left active. 3-4 days on it all settled down
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