Automatic registration for hosts without DNS A record

[eofster]

The automatic SIP registration for the account after launch relies on the macOS network reachability mechanism. And this, in turn, relies on the existence of a DNS A record when a hostname is used. Some time ago, Telekom, the German phone provider, stopped using DNS A record for its hostname tel.t-online.de and started to rely only on the SRV record instead.