Know how
Learn about the email terms and technologies that relay uses.
DKIM
Cryptographic signature for outgoing email
DMARC
Email authentication policy for SPF and DKIM
MTA-STS
Enforce TLS for incoming mail connections
MX
Mail exchange records for domain email routing
PTR
Reverse DNS lookup for IP verification
Return-Path
Bounce address for email delivery notifications
SMTP
Protocol for sending email between mail servers
SPF
DNS record listing authorized sending servers
TLS-RPT
Reports about TLS connection failures