Exchange Online Mail Enabled Users redirecting to eternal SMTP

[Ian_Culliver]

Hi all,

I have a client that has been using Ex2010 and has used mail contacts object to effectively build a reverse DL. They have say 30 Unique contacts with a proxy address inside their Org, but use the External Email Address field to send to the same SMTP.

For example, a user contact called Bill Smith with an internal address of bill@internal.comany.com but the external address of service@companya.com

They then have Jane Doe with an internal address of jane@internal.comany.com but the external address of service@companya.com

So essentially the GAL allows staff to find Bill or Jane and send to them but it goes to a single external mailbox.

Exchange Online will not allow this bad behaviour for obvious reasons but I notice there is an Attribute in MailEnabled Users for "ForwardingAddress" that I can't use or write to. Does anybody know if ;

a) Can I write an external address to this attribute to replace the above behaviour or

b) a way to accomplish the same?

I know I can write a transport rule that redirects from contact Jane Doe with an internal address of jane@internal.comany.com to a Contact object of service@companya.com but this is not only messy for the number involved, but will it not also potentially cause issues with SPAM detection engines?

If there are any ideas, I would love to hear them.

Thanks

[#2 · Accepted solution]

Exchange Online does not enforce uniqueness of the ExternalEmailAddress property, so you should have no trouble doing this:

[10:23:47]# Get-MailUser MU* | ft Name,Primary*,Externa*

Name PrimarySmtpAddress           ExternalEmailAddress
---- ------------------           --------------------
MU1  MU1@michev.info              SMTP:external@domain.com
MU2  MU2@michev.info              SMTP:external@domain.com

Just make sure you create them with different PrimarySMTPaddresses (use the relevant parameter for new-mailuser).

[#3]

@Vasil Michev Thanks you so much Vasil, This works perfectly well as long as you stay away from the GUI and force the PrimarySMTP as you said. I was missing that step.