I'm inferring that you recently upgraded from 8.5.x to 9.0.x ? What version are you running (server and client)?

Did you upgrade the user's mail template as well?

I vaguely remember that issue early in the 8.5 codestream but don't believe that I've ever seen it in any version of 9.0.1.

Hello Mark, thanks for your response. No, that's the strange part. This client (and server, for that matter) has been 9.0.1 for years. The mail template was and remains MAIL9.NTF. The only change was flipping the old domain, call it abc.com, to an alias versus the primary domain (nor 123.com, for example) in the Global Domain Document. The only change to the Person Document was the Internet Address field (changed to new domain, for example user@123.com vs. user@abc.com). Inbound mail gets delivered to both addresses, as desired of course, and outbound mail has the correct address. I cannot figure out why "Reply To All" places the address in the cc: field. I don't think it happens when mobile client (Traveler/Verse) is used, just the Notes client. Any ideas?

You changed your primary internet domain from 'abc.com' to '123.com'.

On the Global Domain document, the field 'Local primary Internet domain:' used to say 'abc.com', now it says '123.com'

The field 'Alternate Internet domain aliases:' used to include '123.com', now includes 'abc.com' (and 123.com is no longer listed in the alias field).

Each Person document 'Internet address:' field was changed from 'user@abc.com' to 'user@123.com', and 'user@abc.com' was added as an alias (typically to the shortname field or fullname field).

So far correct?

Questions:

1) I assume you've rebooted the server?

2) Your Domino domain name - does in include '.com' or a period at all? Or is it strictly alpha characters?

3) For any user that experiences this problem, do every one of their local address book 'Location' documents contain their new email address, 'user@123.com'?

4) Does this happen on every email received, or does it happen perhaps only on emails that the user received to their 'user@abc.com' alias? (and they're replying from user@123.com') ?

5) What specific version is the Domino server? 

6) Specific version of affected user?

that's all i can think of at the moment...

First off, apologies to Mark for the delay in responding. You posed some great questions. I answered below, just in case. The user hasn't reported the issue again but that doesn't mean the problem doesn't persist. I'll reach back out this week. Have a great day.

1) I assume you've rebooted the server? Yes, great question, booted several times since posting

2) Your Domino domain name - does in include '.com' or a period at all? Or is it strictly alpha characters? Domain name does not include .com

3) For any user that experiences this problem, do every one of their local address book 'Location' documents contain their new email address, 'user@123.com'? Impacted user has only one local address book and the location document has the new address.

4) Does this happen on every email received, or does it happen perhaps only on emails that the user received to their 'user@abc.com' alias? (and they're replying from user@123.com')? The issue only occurs when mail is addressed to their old address.

5) What specific version is the Domino server? Domino version is 9.0.1.9

6) Specific version of affected user? Notes client is 9.0.1.9, too.