When using SMTP instead of Outlook in the Email setup within the My Company Info and Settings section of WorkSpace, you’re required to select an SMTP port. If the email service your configuring is Gmail, or your own domain hosted by Google, your choices are 465 or 587.
587 is the Outgoing server (SMTP) port for IMAP. It uses a TLS encryption connection. 465 is the Outgoing server (SMTP) port for pop. It uses an SSL encryption connection.
Enter the appropriate port for the protocol you’ve configured your Gmail account to use (Pop or IMAP).