TKL appliances have a basic (outgoing) mail server built in and by default deliver mail directly themselves no need for SMTP server).
In my experience that generally works really well OOTB but there can be issues. Firstly some ISPs will block the standard mail port (25) on non-business internet plans (thus blocking outgoing mail). Also depending on the email recient's email host emails can sometimes be incorrectly blacklisted...
Oh ok, so you are routing through another server then?
TKL appliances have a basic (outgoing) mail server built in and by default deliver mail directly themselves no need for SMTP server).
In my experience that generally works really well OOTB but there can be issues. Firstly some ISPs will block the standard mail port (25) on non-business internet plans (thus blocking outgoing mail). Also depending on the email recient's email host emails can sometimes be incorrectly blacklisted...