Looks like Comcast's public-facing DNS servers aren't responsive. MXToolbox and a couple other DNS-related sites confirm this, but a simple dig +trace is sufficient as well. $ dig +trace pop3.comcast.net {snipping for brevity} ;; Received 1173 bytes from 192.203.230.10#53(e.root-servers.net) in 11 ms comcast.net. 172800 IN NS dns101.comcast.net. comcast.net. 172800 IN NS dns102.comcast.net. comcast.net. 172800 IN NS dns103.comcast.net. comcast.net. 172800 IN NS dns104.comcast.net. comcast.net. 172800 IN NS dns105.comcast.net. comcast.net. 86400 IN DS 40909 5 2 30C0F50E68DCC9A2F279A994C07CF22CED97AADF44C2B1FE38A1B32B A1A34174 comcast.net. 86400 IN DS 40909 5 1 DDC19733884EE533B35B4B57717BEA9B0EF2C4D1 comcast.net. 86400 IN RRSIG DS 8 2 86400 20230404061502 20230328050502 27254 net. btO4iRmoCjqgYlgZPCORiX7soM6Twg610wTSCdD/sxizsoLoWeB+vBXY mChMJmrhGenkhJroQoriY1FyMDl4EvcTyKRDYG3c8HL0p8ILo4kJAOWi CSAt/qB76i21+8SmLsvhE0bPuUUQQXv69vfDfjxxYVsAbbMGfTLvHNJT BX3B6CrqNzXARN2dpDaUsb/8r3i0ve9byu/Sur2vZIYjwg== couldn't get address for 'dns101.comcast.net': not found couldn't get address for 'dns102.comcast.net': not found couldn't get address for 'dns103.comcast.net': not found couldn't get address for 'dns104.comcast.net': not found ;; Received 649 bytes from 192.48.79.30#53(j.gtld-servers.net) in 15 ms -- | Jeremy Chadwick jdc_at_koitsu.org | | UNIX Systems Administrator PGP 0x2A389531 | | Making life hard for others since 1977. |