How to Setup SMTP Relay in Office 365 - LazyAdmin

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Every place a page here uses this source, in the order the words come in it.

1. “You don’t want to use a mailbox (with username and password) for this, but preferable an SMTP server that sends the mail for you.” The problem with SMTP Authentication these days is that we want to use MFA on all our Office 365 accounts. When we create a dedicated mailbox for sending emails, we still can’t authenticate (and secure) it properly. This is also the reason that Microsoft doesn’t support SMTH AUTH anymore for new tenants created after 2020.

   In Third-party sender authentication

2. Sending emails from a scanner or web application can always be challenging. You don’t want to use a mailbox (with username and password) for this, but preferable an SMTP server that sends the mail for you. This is where we can use SMTP Relay in Office 365. “When we create a dedicated mailbox for sending emails, we still can’t authenticate (and secure) it properly.” SMTP Relay, on the other hand, allows applications and devices to send email through your Exchange Online mail server. Protection is done based on your public IP Address(es), allowing only applications and devices from your network to use the SMTP Relay connection.

   In Third-party sender authentication

3. SMTP Relay vs Direct Send in Office 365 “Because both use the MX endpoint as an SMTP server address, but they both have their own use case.” Direct Send in Office 365 is used to deliver email to only your internal mailboxes. This means that you can’t scan a document and email it directly from the scanner to an external email address. You will need to scan it to your own mailbox, and in Outlook forward it to the external contact.

   In SMTP and email API providers

4. SMTP Relay on the other hand can be used to send emails directly to external contacts, but only from networks (public IP addresses) that you have defined. “Support externally hosted applications Yes No” If you can’t use port 25, then your only other options are SMTP Auth client submission, which uses OAuth for authentication, or a third-party tool like SMTP2GO. The advantage of this tool is that you can use different port numbers, like for example port 2525, or even port 80, and simply authenticate with a username and password.

   In SMTP and email API providers

5. “You don’t want to use a mailbox (with username and password) for this, but preferable an SMTP server that sends the mail for you.” The problem with SMTP Authentication these days is that we want to use MFA on all our Office 365 accounts. When we create a dedicated mailbox for sending emails, we still can’t authenticate (and secure) it properly. This is also the reason that Microsoft doesn’t support SMTH AUTH anymore for new tenants created after 2020.

   In SMTP and email API providers

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