Hello @robertkwild
I haven’t been able to test this personally but have been meaning to get an open SMTP relay on the network for this. My current lab setup connects directly to my hosted email service so auth and TLS is required.
I did find this however, so presumably so long as you can verify SMTP to your relay service can be sent from your BW host machine, you should be able to just leave the fields blank for Bitwarden to sent to your SMTP relay and recieve emails from your self-hosted instance!