How can an exchange account that is disbaled, send out a meeting request?

We have a user that was let go from the company so we disabled their AD and Exchange (exch 2013) account but for some reason today, they disabled account sent out a meeting request...
How could this be and how can we stop this from happening?
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Murali ReddyExchange ExpertCommented:
Mailbox disabled (disconnected) or just AD account disabled?

If just AD account is disabled I see two possibilities-

1- There shall be a delegate with SendAs or sendon behalf rights sending this invite intentionally or unintentionally.

2- An old meeting request where the organizer is the so called disabled user, is updated by respective user delegates.

or there is a also a possibility that a synced device (ActiveSync) involved here.
vmichAuthor Commented:
The AD account was disabled which in turn should disable the exchange account correct?
Murali ReddyExchange ExpertCommented:
That is a wrong perception. Disabled AD account will deny the user to interactively logging in to the mailbox. However the mailbox is still functional and can receive emails. Delegates can work on behalf of the mailbox (and hence the email address).
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vmichAuthor Commented:
Well I just checked the account in exchange and it appears that it is saying it is disabled..
How can I be sure it is disabled in exchange which I think it is?
Murali ReddyExchange ExpertCommented:
simple - You send a test mail, it will not shoot any NDR. Check your tracking log, the message is delivered to the mailbox.
Will SzymkowskiSenior Solution ArchitectCommented:
If the mailbox is DISABLED, then it will not appear in the EAC or Powershell. This mailbox will be in a Disconnected State if the mailbox is disabled. If it is only the AD Account that is disabled then mailbox is still active as Murali has already mentioned.

If you had calendar items that were stuck in the Outbox or delayed sending this could also be another reason why it was sent out.

vmichAuthor Commented:
I found the issue.. We were not given all of the information first by the users... Go figure!!!
The reason this was happening is that users were forwarding these meeting request they had on behalf of the users who was no longer with the company...

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vmichAuthor Commented:
forwarding users meeting request
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