Adding alias to an Office 365 mailbox with dirsync

active-directorymicrosoft-office-365

We've recently migrated to Office 365 with a new Active Directory structure and as part of this the naming convention for all the e-mail addresses has changed. This isn't a problem for most users, but some users have stationery with their old style e-mail address so we need to add these address as aliases for these users.

Because we use DirSync, we can't edit the mailboxes directly in Office 365. I found some instructions online which said to add the additional addresses to the ProxyAddresses field in Active Directory. I've done this, but now the address I've added to ProxyAddresses is showing up as the primary SMTP address in O365.

How can I add an alias without this alias becoming the primary SMTP address?

UPDATE:

I didn't realise that this was case sensitive, so I've updated all the users that I changed with "smtp" lower case. Now the primary SMTP address is the user@domain.onmicrosoft.com address, which I also do not want.

Can't upload a screenshot presently due to being at work, but here is what it would show:

In Office 365:

SIP:user@mydomain.com

SMTP:user@mydomain.onmicrosoft.com

smtp:user@mydomain.com

smtp:alias@mydomain.com

Entries in bold are primary addresses. The primary SMTP address should be user@mydomain.com.

In Active Directory, the ProxyAddresses field contains the following data:

smtp:alias@mydomain.com

For a user that does not have an alias (the ProxyAddresses field is empty), Office 365 shows the following:

SIP:user@mydomain.com

SMTP:user@mydomain.com

smtp:user@mydomain.onmicrosoft.com

Best Answer

Inside ADSIedit under the ProxyAddresses field is correct.

You want the primary one to be preceded by SMTP: in all caps. In this case set it as SMTP:user@domain.com

The secondary/tertiary ones should be preceded by smtp: all lowercase. In this case set it as smtp:useralias@domain.com

Make sure the mail attribute in their user account in AD (the one on the General tab that says "E-mail") has the user@domain.com email address as well.

After a dirsync it should show an additional proxy address synced over as the "onmicrosoft.com" one but with lowercase smtp:

Also note, that if your domain hasn't been "verified" in Office 365 then it will revert back to using the onmicrosoft.com address.

Let me know if that works for you.

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