I have email that refuses to send to a vendor I use.
I have TLS required on all outbound email. I have a couple of connectors allowing non-TLS to certain people.The recipient mail server accepts TLS according to MXToolbox.
The error message is UntrustedRoot
Reason: [{LED=450 4.4.317 Cannot connect to remote server [Message=UntrustedRoot] [LastAttemptedServerName=snowflakem-d.com] [LastAttemptedIP=66.96.140.92:25] [BN7NAM10FT007.eop-nam10.prod.protection.outlook.com]};{MSG=UntrustedRoot};{FQDN=snowflakem-d.com};{IP=66.96.140.92};{LRT=8/12/2020 8:55:47 PM}]. OutboundProxyTargetIP: 66.96.140.92. OutboundProxyTargetHostName: snowflakem-d.com
I made a connector to not require TLS and I also tried Require TLS but allow any cert (even self signed). But it still gives this error.
The MX Lookup says the IP belongs to the Endurance group which owns things like hostgator https://www.endurance.com/our-brands