Office 365 supports SMTP relay for authenticated accounts using TLS encryption.
Testing SMTP access is traditionally done using Telnet, but that’s not always an option when using Office 365 due to the authentication requirement.
Fortunately it’s easy to use PowerShell to accomplish the same thing.
How to test SMTP server using PowerShell:
Capture and store the Office 365 credentials for the account you intend to use for SMTP auth:
$msolcred = get-credential | save the credential of from address
Use the stored credentials to send a test message from firstname.lastname@example.org to email@example.com, over port 587 (Encrypted w/ SSL):
Send-MailMessage –From firstname.lastname@example.org –To email@example.com –Subject “Test Email” –Body “Test SMTP Relay Service” -SmtpServer smtp.office365.com -Credential $msolcred -UseSsl -Port 587