My mistake. I was looking up the SRV record for _sip._tcp.grepular.com and assumed that the reason it failed was because it didn't support SRV. The failure was

My mistake. I was looking up the SRV record for _sip._tcp.grepular.com and assumed that the reason it failed was because it didn't support SRV. The failure was the underscores though, which you've now fixed.