Exchange/Office 365 - Mail Contacts surprise!

[mdrabble]

Our governors use their personal email addresses for their Governors roles (even though I have said school email addresses would be better as more secure etc)..... anyway.... let me carry on.

 

We have their personal email addresses entered onto Exchange/Office 365 as mail contact, so these can be put into a governors email distribution group and works ok.

 

They do not have a school email address or any aliases in place....

 

However.... one of the governors has been in contact with school to complain about some emails being set to him from companies as if he has an school email address.

 

His email address is blah@ntlworld.... and emailed being sent to him are addresses as name@schooldomain

 

 

So this came as a bit of a shock to learn that Exchange/Office 365 is doing some kind or translation and forwarding on emails to his personal email account even though no school account/aliases exist or any settings in place to forward emails.

 

I've now put mail rules in place to block external senders from sending emails to these mail contacts.

 

 

Anyone come across this before?

[MatthewL]

Firstly get a copy of the message header of one of the said messages and analyse it.

 

Secondly when you add a contact it will create an alias of [email protected] (for example) so in theory it would look as if they had a corporate address and someone may have guessed the email unless that address has been used in the past? Things in the past worked like that in Exchange, although cannot say I've looked at O365 from that side as had no need to but worth checking what SMTP addresses are on the account.

[3s-gtech]

Has it used their mail.onmicrosoft.com address held in M365? Basically the alias used by the tenant, and a big part of Hybrid.

 

If so, that may have leaked or been guessed. External senders should never need to send to that, but make sure your Exchange server has clearance to do so.

[chaplic]

Sounds like you've created mail enabled user rather than a mailcontact...?

 

Or you have created some sort of DL or dynamic DL containing the contact.

 

What does a message trace produce?