Replyto address

When I send out an e-mail to an external user the replyto address of other internal users are not formatted properly. I.e,

From: me/abc/corp

To: user@123.com, xx/abc/corp, yy/abc/corp

external user, user@123.com, clicks on reply to all and the addresses are formatted like this:

From: user@123.com

To: me@corp.com, xx/abc/corp@corp.com, yy/abc/corp@corp.com

I’ve checked the usual suspects, like the Internet Mail Address field in the Location Document, and the Person Document in the DD but both are OK.

Can anyone shed some light on this?

ST