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DieterTontsch-0908 avatar image
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DieterTontsch-0908 asked DieterTontsch-0908 commented

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

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://docs.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

office-exchange-server-administrationoffice-exchange-online-itprooffice-exchange-server-mailflow
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1 Answer

KyleXu-MSFT avatar image
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KyleXu-MSFT answered DieterTontsch-0908 commented

@DieterTontsch-0908

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:
202088-d5c5a7fa-aba4-4bf4-976f-4c7128fcab2d.png

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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Yes, but wouldn't it be ok to use Exchange Online Shared Mailboxes which do not consume, up to a certain level, a license? At least in my tests this works fine with a shared mailbox, though.

Despite the problem with From-Addresses, but if this issue is not on topic, is a shared mailbox a thing we could go for?

thanks
Dieter

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KyleXu-MSFT avatar image KyleXu-MSFT DieterTontsch-0908 ·

Using a dedicated mailbox for relay is Microsoft suggestion.

If shared mailbox could work in your tenant and meet your requirements. You could keep use it.

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For now it works, but that shared mailbox isn't yet alive in EXO since more then 30 days. So, it might still bekomme a licensing issue after the 30 days. But for now it works. It does not suite the several from address topic, but for some dedicated senders, mainly some which are outside the organization and rely on SPF and DKIM, it should be a solution.
thanks,
Dieter

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