Outlook configuration in Google terminal server environment depends on the service that is being used for email.
​Office 365 and Exchange don't require any special configuration and can be set up relatively easily.
​
imap and Pop3 need additional outside configuration due to port blocks from Google. Google doesn't allow outbound connections on ports 25, 465 and 587. Of those ports, only port 25 is permanently blocked. These ports are very susceptible to abuse and that's the reason Google blocks them.
​
However, there are options you can look at in order send emails out through third party email services. Please have a look at the link to the Google documentation referencing the limitation as well as other options in order to get emails out:

https://cloud.google.com/compute/docs/tutorials/sending-mail/