How to properly configure Outlook for Windows to default Send From a Shared Mailbox?

Iron Contributor

For security reasons, I'm trying to move our organization away from using "serviceATdomainDOTcom" as Exchange User Accounts. These are accounts such as "payments", "contracts", "vendors", etc.  

Instead, I want these service accounts to be used as Shared Mailboxes which I can provide access to for each user who authenticates with their own email account.  Service accounts should be disabled from sign in Azure to prevent malicious attacks / usage.   

Most of the people involved with these accounts are our office / admin staff who tend to be stuck using the Old Outlook for Windows - please consider this with your responses as New Outlook works differently. 


So we have userATdomainDOTcom and serviceATdomainDOTcom. The user is signed into Outlook / M365 with their userATdomainDOTcom account and sees the serviceATdomainDOTcom Shared Mailbox below their account.  


The first issue we're having is that SENT items are in the user's sent folder, not the Shared Mailbox account's sent folder.  


The second issue I'm observing is that our CodeTwo email signatures are coming from the user account, not the Shared Mailbox account. I have confirmed by resetting the license account in CodeTwo that this service account does have a license.  


Finally, just to verify, because the account the user is primariuly going to use is a Shared Mailbox that's disabled as an account in Azure and not a User account, it's not possible to make it the Default account in Outlook? Although, I've just discovered a setting in Options > Mail > Send Messages "Always use the default account when sending new messages" which I hope will resolve this. 

1 Reply
The easy way to solve all three issues is to configure the shared mailbox as additional account in Outlook (i.e. remove Automapping and add it via File > Add account and providing the credentials of the user with Full access permissions when asked). This will allow Outlook to treat it just like any other "regular" mailbox and enable all functionalities, including add-ins. If you need detailed steps, read here:

If for some reason you don't want to do this, you can address #1 server side, by configuring the MessageCopyForSentAsEnabled property. There's also a client-side method, both detailed here:

#2 is likely by design, but best confirm with the vendor. Or, configure the mailbox as additional account :)

#3 will only work if you configure it as additional account, otherwise you will have to manually select the From address each time.