If you want to send an email to a third-party application or if you're going to send an email to people inside and outside your organization, setting up SMTP in Microsoft email is the way to go.
For Outgoing server settings, click Outgoing server requires authentication.
Click the radio button next to Use the same settings as the incoming server.
Click Close and Finish.
You can now use Office 365 with SMTP configured and Setting Up SMTP In Microsoft Email is completed.