Exchange 2016 External Email Random Issue

[ITGURU]

I am running on-premise Exchange 2016 server and randomly/occasionally I have an issue with emailing external email addresses.

 

On the first send I get an undeliverable with:

 

Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup'

 

However, if i re-send or go to my sent items - re-select the email address, the email then delivers the second time.

 

Has anyone seen this before, or know why it should be a sporadic issue, when the external email addresses are not even part of the same email organisation.

 

It doesnt happen on all emails, and sometimes I can send to the same recipient and it will go the first time.

 

 

Thanks.

[3s-gtech]

Using Outlook client or Outlook on the Web?

[ITGURU]

Using Outlook client or Outlook on the Web?

Full version of outlook 2016

[3s-gtech]

This can be caused by a couple of things in Outlook - https://docs.microsoft.com/en-us/exchange/troubleshoot/connectors/exrecipnotfound-ndr

 

Can you test from OotW?

[ITGURU]

This can be caused by a couple of things in Outlook - https://docs.microsoft.com/en-us/exchange/troubleshoot/connectors/exrecipnotfound-ndr

 

Can you test from OotW?

 

I'd have to always email from OWA to test. Every time i send the email i always use the autocomplete entry, sometimes it goes, sometimes it doesnt. I've even removed the autocomplete entry and typed the email afresh .

Difficult to test, as sometimes i can go ages with using the autocomplete entry and it's been fine, then one time i use it, it fails and have to re-send.