Shared Mailbox are email addressess that do not posess their own Microsoft 365 licenses, but rather let anyone with a license access and act on their behalf.
✅ Send as a Shared Mailbox (via your personal mailbox)
First off: You can use SecureMailMerge to send on behalf of a Shared Mailbox (just as with any alias) if your Microsoft 365 tenant has been setup this way. All you need to do is:
- create a new email in your personal mailbox, then
- change the "From" address in the Email composer window to the Shared Mailbox address, and
- then create a campaign with SecureMailMerge.
( If you don't see the From field, click the "Show From" button in the ribbon.)
But there is a drawback to this "Send As" approach: The email will be sent from the Shared Mailbox, but the email will be saved in your Sent Items folder. This is because the email is sent from your account, not the Shared Mailbox account. Recipients will see the sender as the shared mailbox and any replies will go to the Shared Mailbox.
❌ Send from Shared Mailbox directly
Support for Outlook Add-Ins in Shared Mailboxes is limited and this scenario is not supported unfortunately as it would require installing the add-in for the shared mailbox (vs. installing it for your personal mailbox). This is not unique to SecureMailMerge, no other plugins can offer this features either as far as we know. Microsoft is constantly working on making more functionality available but as of writing there is not ETA when this use case will be available.