Guides about email verification, SMTP and mail servers.
What an email server actually is - the MTA, MDA and mailbox roles - and the software that runs them: Postfix, Exim, Sendmail, Microsoft Exchange, Dovecot, hosted Google/Microsoft 365, and the spam gateways in front. Plus how to tell what a domain uses.
Read →How to test a mail server by hand with telnet or openssl: every SMTP command (HELO, EHLO, MAIL FROM, RCPT TO, VRFY, EXPN, STARTTLS, QUIT), response codes, and a full worked example.
Read →Test an SMTP server online without telnet or an open port 25: how this site runs the live SMTP commands (EHLO, MAIL FROM, RCPT TO) for you, when to use an online test vs a manual smtp telnet test, and how to read the response codes.
Read →How web servers display your mail (webmail) and power communication with users (contact forms, confirmations) - the main software (Nginx, Apache, LiteSpeed, IIS, Caddy), and why the website and the mail server are separate.
Read →What the raw source of an email really contains - every header explained (From, Reply-To, Return-Path, Message-ID, Received, DKIM), the MIME variables (Content-Type, boundary, charset, Content-Transfer-Encoding, Content-Disposition), and how base64 / quoted-printable and multipart parts fit together.
Read →A practical, step-by-step setup guide for your own domain: build one SPF record (and the 10-lookup limit), enable DKIM per sender, roll out DMARC safely from p=none to p=reject, keep sending IPs off RBL blocklists, and verify every layer with real headers.
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