How do I turn off auto-appending of @IBMUS,etc. to addresses when replying to mail?

In the last few months whenever I click Reply or Reply All to an email it automatically appends @IBMUS or @IBMAU or @IBMCN, etc, to all the email addresses I’m replying to. If any of these addresses is a contact group it won’t send properly and I have to re-send the email to them if I forgot to manually delete the @IBMXX from the address. I think this must be a new feature or a new bug, so how do I turn this off?

Thanks,

Alex

Subject: Speak to your internal IBM support folks

This is a setup by IBM admins. You’ll need to speak to them,