Hey @emendoza,
We have an open feature request around this right now. Not an uncommon ask and it is something we plan on supporting (there are some compliance issues we need to make sure we can support). Many customers get around this limitation using SendGrid. It is a free service exclusively designed to do this specifically. Here is a guide on how to set that up in Tulip.
Internal distribution lists are often something that can’t be emailed from an external email (which is how Tulip/SendGrid send emails) so this is a bit of a trickier ask. I came from a customer who used rules in outlook to do this forwarding, so all emails went to one email, and rules forwarded emails to that internal-only group. In the future, Tulip could build functionality to connect directly to your mail server, so it could send to any groups an internal user could, but this is a significantly bigger ask, and gets quite technical to setup very quickly.
Hope this helps,
Pete