SMTP

SMTP transport, STARTTLS, MTA-STS, and TLS reporting.

Featured articles

How SMTP Email Delivery Works: From EHLO to Queue and Delivery
SMTP is the store-and-forward protocol mail servers use to transfer messages. A sending server finds the …

All SMTP articles

How SMTP Email Delivery Works: From EHLO to Queue and Delivery
SMTP is the store-and-forward protocol mail servers use to transfer messages. A sending server finds the …
Check your domain's email security

Run the free Email Security Score to see how your domain's SPF, DKIM, DMARC, and DNS setup actually looks.

Run the free Email Security Score

Related topics

Email Authentication
How SPF, DKIM, and DMARC work together to prove an email really came from your domain.
SPF
Sender Policy Framework: syntax, DNS lookup limits, permerror, and common misconfigurations.
DKIM
DomainKeys Identified Mail: selectors, signing, alignment, and key rotation.
DMARC
DMARC policies, alignment, and aggregate/forensic reporting.
DNS
The DNS record types and concepts email authentication and delivery depend on.
Deliverability
Why legitimate email ends up in spam, and how to keep it out of it.
MXFend

Free email deliverability tools for domains.

Tools
Email Deliverability Checker SPF Checker DMARC Checker MX Checker
Guides
Knowledge Base Email auth guide Emails going to spam Domain reputation SMTP TLS MTA-STS TLS-RPT
Company
About Contact Privacy Terms Refund Policy
© 2026 MXFend. All rights reserved.