How to Send from Outlook Using SMTP
Postmark can be used to send emails from Outlook using SMTP without affecting the ability to receive emails at the email address using its existing IMAP configuration. In this help article, we show you how to configure your Outlook desktop client so that outbound emails from your Outlook account are sent via Postmark. This help article uses Outlook for Mac 2016 for screenshots. The exact views may differ for other versions of Outlook.
Access Account Settings
Configure Outbound Settings