email relay for application

Question

Hi All

I am using exchange 2016 hybrid environment. Our application users are using anonymous relay i.e our application users in their application to trigger emails use the relay m.mydomain.com on port 25. Now i want to come up with authenticated relay. i.e i want to create service accounts for the application users so that they can use it in their application for example. m.mydomain.com on port 587 or smtp.office365.com on port 587.

i have few queries here. i have an AD group for service accounts which is synchronized to Azure AD.

Now if a user uses internal relay m.mydomain.com on port 587, i will create a service account which will be synced to azure AD does this account needs to have a mailbox with license. here the user will just use for authentication. if the user uses smtp.office365.com does a mailbox is required.

if the user needs service account also for receiving the emails then i can create mailbox with exchange license. Does this account needs to have POP3 and IMAP enabled.

Answer 1

Hi @Rising Flight

if the user uses smtp.office365.com does a mailbox is required.

Yes. You may need a mailbox with Exchange license assigned to it.

Does this account needs to have POP3 and IMAP enabled.

It isn't necessary but depends on the client you are using.
For example if you are using Outlook, you may use Mapi over Http to access the mailbox.
However, if you are using clients which only support POP3 or IMAP4, you may need to enable it.
(by default it is enabled for all users unless you have security defaults enabled).

In addition, if you would like to enable SMTP relay, you may also need to disable security defaults.
For more detailed information on how to setup SMTP relay, please refer to Option 1 in this link:
How to set up a multifunction device or application to send email using Microsoft 365 or Office 365

If you run into problem with sending emails, please refer to this link for troubleshooting:
Fix issues with printers, scanners, and LOB applications that send email using Microsoft 365 or Office 365

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