Is a Shared Mailbox enough (and the right approach) in Exchange Online for SMTP only

Question

Hello,
I wonder if a Shared Mailbox, which from what I understand obviously needs an Azure Account, but no Exchange License (at least when I'm fine with a few limitations) is enough in order to use it as SMTP gateway for third-party applications. We come form Exchange on-prem where an AD user didn't necessarily was required to have an Exchange Mail-Box, ms-Exch-SMTP-Accept-Authoritative-Domain-Sender permission on a certain SMTP Connector was enough.

Therefore we have several applications which need to use SMTP, internally and world-wide. This post https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-microsoft-365-or-office-365 does not really sas clear what the minimum requirement for an AzureAD/Exchange user is in order to use it for third-party SMTP.

From what I figured, a shared mailbox + send as permissions on certain mailboxes/distribution lists in charge, seems to work for me. But is this the right approach to go, at least if I do not want to receive Emails on such addresses?
And also, in the on-prem world we didn't have to deal a lot with the From Address, any Address was accepted and emails got delivered, at least internally. Is it required to have a mailbox or distribution list + send as for each and any from address I'd like to use? Thinking of printers or other devices, there is no need for a reply on those notification emails....

thanks in advance,
Dieter

Answer 1

@Anonymous

For Exchange online relay emails, you need to use an Office 365/Exchange online mailbox to relay emails. You could see from the picture contained in the article that you find:

And also, in the on-prem world we didn't have to deal a lot with the From Address, any Address was accepted and emails got delivered,

Yes, for Exchange online you need to use your own email address (verified in Office 365) to relay emails.

So, for saving license and could send mail through virtual email address, it is suggested you keep Exchange on-premises for relay emails for applications such as printers.

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