The resolve method disables resolving relative names by default. This change probably makes a7710e90 unnecessary. @JoshData added some additional changes from query to resolve.
Port 465 with "implicit" (i.e. always-on) TLS is a more secure approach than port 587 with explicit (i.e. optional and only on with STARTTLS). Although we reject credentials on port 587 without STARTTLS, by that point credentials have already been sent.
Rauno Moisto
Joshua Tauberer