I'm unable to reach the SMTP service on us-smtp-inbound-1.mimecast.com or us-smtp-inbound-2.mimecast.com from multiple markets: Dallas, Denver, Phoenix. I can reach them from Atlanta and Seattle. They are reachable on at least one address in Los Angeles, unreachable on others. Dallas: $ telnet us-smtp-inbound-1.mimecast.com 25 Trying 205.139.110.221... Trying 207.211.30.221... Trying 207.211.30.141... Trying 205.139.110.141... Trying 205.139.110.242... Trying 207.211.30.242... telnet: Unable to connect to remote host: Connection timed out Denver: $ telnet us-smtp-inbound-1.mimecast.com 25 Trying 207.211.30.221... Trying 207.211.30.242... Trying 207.211.30.141... Trying 205.139.110.242... Trying 205.139.110.221... Trying 205.139.110.141... telnet: Unable to connect to remote host: Connection timed out Finally found one host in LA that worked after two failures: $ telnet us-smtp-inbound-1.mimecast.com 25 Trying 205.139.110.221... Trying 205.139.110.141... Trying 207.211.30.242... Connected to us-smtp-inbound-1.mimecast.com. Escape character is '^]'. 220 us-smtp-1.mimecast.com ESMTP; Tue, 03 May 2022 12:38:11 -0400 QUIT 221 Service closing transmission channel [uajtgwEROGqfo99gP4hQyg.us397] Connection closed by foreign host. $ mtr -r -c3 -w 205.139.110.221 Start: 2022-05-03T10:43:06-0600 HOST: los-angeles Loss% Snt Last Avg Best Wrst StDev 1.|-- LA624-C6504-1-VL624.massivenetworks.net 0.0% 3 0.6 0.5 0.5 0.6 0.1 2.|-- 199.45.152.18 0.0% 3 0.4 0.4 0.4 0.4 0.0 3.|-- xe-10-0-0.edge1.LosAngeles9.Level3.net 0.0% 3 4.7 2.0 0.6 4.7 2.4 4.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0 5.|-- MIMECAST-SE.ear1.NewYork6.Level3.net 0.0% 3 68.8 68.8 68.7 68.8 0.1 6.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0 $ mtr -r -c3 -w 207.211.30.242 Start: 2022-05-03T10:47:11-0600 HOST: los-angeles Loss% Snt Last Avg Best Wrst StDev 1.|-- LA624-C6504-1-VL624.massivenetworks.net 0.0% 3 0.6 0.5 0.4 0.6 0.1 2.|-- 199.45.152.18 0.0% 3 0.4 0.4 0.4 0.5 0.1 3.|-- et-0-0-6-2.cr4-lax2.ip4.gtt.net 0.0% 3 0.4 0.5 0.4 0.6 0.1 4.|-- ae23.cr3-lax1.ip4.gtt.net 0.0% 3 1.3 1.3 1.1 1.3 0.1 5.|-- ae-3.r01.lsanca07.us.bb.gin.ntt.net 0.0% 3 1.3 1.2 1.2 1.3 0.1 6.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0 7.|-- ae-3.r24.snjsca04.us.bb.gin.ntt.net 33.3% 3 15.4 13.7 12.1 15.4 2.4 8.|-- ae-8.r23.chcgil09.us.bb.gin.ntt.net 0.0% 3 57.3 58.0 57.3 58.9 0.8 9.|-- ae-0.r22.chcgil09.us.bb.gin.ntt.net 0.0% 3 64.4 61.5 58.9 64.4 2.8 10.|-- ae-6.r21.nwrknj03.us.bb.gin.ntt.net 0.0% 3 69.7 71.2 69.4 74.6 2.9 11.|-- ae-11.r01.nycmny17.us.bb.gin.ntt.net 0.0% 3 70.2 70.0 69.8 70.2 0.2 12.|-- ce-0-8-0-3-200.r01.nycmny17.us.ce.gin.ntt.net 0.0% 3 74.9 87.4 74.9 112.2 21.5 13.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0 $ Phoenix: $ telnet us-smtp-inbound-1.mimecast.com 25 Trying 207.211.30.141... Trying 207.211.30.221... Trying 205.139.110.141... Trying 205.139.110.242... Trying 207.211.30.242... Trying 205.139.110.221... telnet: Unable to connect to remote host: Connection timed out $ Seattle: $ telnet us-smtp-inbound-1.mimecast.com 25 Trying 207.211.30.141... Connected to us-smtp-inbound-1.mimecast.com. Escape character is '^]'. 220 us-smtp-1.mimecast.com ESMTP; Tue, 03 May 2022 12:34:04 -0400 QUIT 221 Service closing transmission channel [0EM41sKhMWizUnOQs3cnYQ.us479] Connection closed by foreign host. $ mtr -r -c3 -w us-smtp-inbound-1.mimecast.com Start: 2022-05-03T10:37:23-0600 HOST: seattle Loss% Snt Last Avg Best Wrst StDev 1.|-- 204.144.179.129 0.0% 3 0.4 0.4 0.4 0.5 0.0 2.|-- 9-1-4.ear1.Seattle3.Level3.net 0.0% 3 0.5 0.6 0.5 0.7 0.1 3.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0 4.|-- MIMECAST-SE.ear1.NewYork6.Level3.net 0.0% 3 76.6 76.6 76.5 76.7 0.1 5.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0 $ Atlanta: $ telnet us-smtp-inbound-1.mimecast.com 25 Trying 207.211.30.242... Connected to us-smtp-inbound-1.mimecast.com. Escape character is '^]'. 220 us-smtp-1.mimecast.com ESMTP; Tue, 03 May 2022 12:08:11 -0400 QUIT 221 Service closing transmission channel [M0wFRdZ-NhONlAOBhS22Sg.us227] Connection closed by foreign host. $ mtr 207.211.30.242 -w -r -c 3 Start: Tue May 3 10:17:58 2022 HOST: atlanta Loss% Snt Last Avg Best Wrst StDev 1.|-- Atl55-C6504-1-VL412.massivenetworks.net 0.0% 3 0.3 0.4 0.3 0.7 0.0 2.|-- 6-2-2.ear3.Atlanta2.Level3.net 0.0% 3 0.3 0.3 0.3 0.3 0.0 3.|-- 4.69.217.206 0.0% 3 17.9 7.3 1.5 17.9 9.1 4.|-- NTT-level3-100G.Atlanta2.Level3.net 0.0% 3 1.1 1.0 0.8 1.1 0.0 5.|-- ae-4.r23.atlnga05.us.bb.gin.ntt.net 0.0% 3 1.3 2.6 0.5 6.0 2.9 6.|-- ae-4.r25.asbnva02.us.bb.gin.ntt.net 0.0% 3 13.0 13.6 13.0 14.2 0.0 7.|-- ae-4.r21.nwrknj03.us.bb.gin.ntt.net 33.3% 3 18.9 18.8 18.7 18.9 0.0 8.|-- ae-11.r01.nycmny17.us.bb.gin.ntt.net 0.0% 3 19.3 19.2 19.0 19.3 0.0 9.|-- ce-0-8-0-3-200.r01.nycmny17.us.ce.gin.ntt.net 0.0% 3 24.8 24.7 24.5 24.8 0.0 10.|-- ??? 100.0 3 0.0 0.0 0.0 0.0 0.0