Mrs W and I have been married for a long time but, until last week, she was still using her maiden name for work. Now, for a variety of reasons, is a good time for her to switch and, as we use Office 365 for her business email, I said “Yeah, it’s really simple; just let me know when you’ve told your contacts about the name change and I’ll switch it over.”

So, when the time came, I changed the display name in the Exchange Online Exchange Admin Center (no changes to her SMTP addresses were needed) and thought that would be it. Nope. Test emails sent came from the original display name. The same happened with another account that I changed the name on. Wondering if this was an Outlook issue, I tried from Outlook Web App: no difference. Test emails were sent back and forth to email addresses outside our Office 365 tenant (like my work account) and the original name stubbornly stuck – I even looked in the message headers and, there it was.

I’m not sure, but I think the issue was related to the offline address book as, the GAL reflected the change immediately but the offline GAL was still showing the old display name.

Unlike in an on-premises Exchange installation, I couldn’t update the address book: connecting to Exchange Online via PowerShell and asking for Get-Command *Offline* told me that the Update-OfflineAddressBook cmdlet is not available in Exchange Online (confirmed in the TechNet reference, which only refers to Exchange Server 2013).

Like so many things in Exchange (and I remember this from my original Exchange 4.0 training course in 1996), it proved to be one issue that’s best left for a few hours to fix itself. The offline GAL updated overnight and emails were then sent with the new display name (not sure why this affected OWA though…).