exchange online: decommission email accounts

Copper Contributor

Dear all.

I am a little bit new to Exchange email but not emails servers in general.


I have had other email servers where, if an email was recieved by the server and there was not an account linked to the name, then it would be automatically stored in a separate account.

I want to know if this is possible with exchange.


In addition, I am also looking for a way to deal with emails sent to users who have left the company.

My first idea was simply to create a mailbox and add each user that has left, as an alias with an automatic reply to inform the sender that they are no longer employed for our company.


I would be so very greatful for any help or guidance.  I have googled, but my search syntax is lacking the correct terms I think.


How do you all deal with licences for email for users that have left and you need to reassign there license to other users?


Many thanks to anyone who can help me get this situation under control or at the very least, help me understand how to deal with it in Exchange.


Many Thanks


3 Replies
Exchange only accepts mail for existing recipients, however you can use transport rules to create a so-called "catch all" mailbox. Considering the amount of spam you will be getting, there's little point into doing this. Here's a sample setup:

As for dealing with leavers, you have two choices: convert to shared mailbox (best solution if you need continuous access) or inactive mailboxes (data is only occasionally accessed, if ever). Here's a comparison:

SortAliasesShared flow for Office 365 can help you with handling emails sent to users who have left the company. Usually a user mailbox of a leaver is converted to a shared mailbox.
To limit the amount of shared mailboxes, you can create only one and assign to it email addresses of leavers as aliases. 


Seems like you have 2 questions on this post.

1) NDR messages for people who left the organization. Do you have a business require for it? Because if not, if someone is trying to send a message to an account that no longer exists, they will get a NDR message. If you have to address it, you have many ways to do it. Like create a generic account and including the aliases for those people who left. Risk is getting to many junk on it.
Take a look at this post:

2) Managing licenses. Some posts.

Hope that helps.