Using Microsoft Outlook 2011 or 2016 for the Mac fails to send


When sending email from Microsoft Outlook 2011 and Microsoft Outlook 2016 for the Mac, it fails to send, produces an error and the email remains in the Outlook outbox.


The cause of this may be due to the outbound SMTP settings configured for the account. If you select Use SSL to connect, this will work differently depending on the port configured. If the port is 465, then Outlook will connect over SSL to the SMTP service to send the email. But if the port is different, for example, port 587, then the connection will be made over non-SSL and then elevated to SSL using the SMTP STARTTLS command.


To resolve, you must either have configured port 465 for SMTP as SSL, or have an alternate port for them, which is not SSL. You are able to enable the Only allow secure authentication option for this alternate port to make sure that they only authenticate over an encrypted connection.


Class:TRB: Troubleshooting (Configuration or Environment)
Revised:Thursday, December 29, 2016