When using Go's smtp.SendMail to send an email to firstname.lastname@example.org, I get the following error:
x509: certificate is valid for mx.zendesk.com, www.mx.zendesk.com, not mail.pod-4.int.zendesk.com
Before calling SendMail, I do an MX lookup on groupsio.zendesk.com, which returns mail.pod-4.int.zendesk.com. So, the address I pass into SendMail is mail.pod-4.int.zendesk.com:25.
This used to work, but something broke and I can't figure out what's wrong. If I send a message to email@example.com from Gmail, it works fine.