README

Minimal POP3 and SMTP servers intended for local account-setup and client integration tests. POP3 serves messages from a filesystem maildir. SMTP accepts messages and relays them using src/mail/Smtp.

This is not for production use.

What it does

• POP3: Listens on a TLS socket (implicit TLS) — default 0.0.0.0:1995.
• POP3: Serves messages from a configurable maildir directory (recursively scanned, oldest first).
• POP3: Accepts any USER/PASS (no verification) — for testing only.
• POP3: Supports core commands: CAPA, USER, PASS, STAT, LIST, UIDL, RETR, TOP, NOOP, RSET, QUIT.
• SMTP: Listens on implicit TLS (default 0.0.0.0:465). Accepts EHLO/HELO, AUTH (accepts any), MAIL FROM, RCPT TO, DATA, RSET, NOOP, QUIT.
• SMTP: On end of DATA, relays via \cryodrift\mail\Smtp using configured user accounts.
• SMTP (receiver mode): Optionally saves each received message to a Maildir so POP3 can serve it.
• POP3: Multi-line responses and dot-stuffing per POP3.

Requirements

• PHP 8.4+
• TLS certificate and key files (self-signed is fine for local testing)
• A maildir-like folder with message files (POP3)
• add domain to hosts eg: 127.0.0.1 mail.lab.lan
• create cert for this domain

Minimal usage examples

POP3

php vendor/bin/cryodrift.php -echo /mailserver/cli/ pop3

SMTP

php vendor/bin/cryodrift.php -echo /mailserver/cli/ smtp

Connecting for quick tests

POP3 over TLS (implicit):

openssl s_client -connect 127.0.0.1:1995 -quiet

SMTP over TLS (implicit):

openssl s_client -connect 127.0.0.1:465 -quiet
EHLO localhost
AUTH PLAIN
MAIL FROM:<test@example.com>
RCPT TO:<dest@example.com>
DATA
Subject: hello

body
.
QUIT

Maildir notes (POP3)

• The server recursively scans the configured maildir and serves every file it finds as a message.
• Messages are sorted by file modification time (oldest first).
• UIDL uses the filename (before any :2, suffix) for stability.

Limitations

• POP3: No user authentication or authorization (accepts any credentials). Read-only (DELE disabled).
• SMTP: Accepts any AUTH and relays based on local account config; intended only for local tests.
• Designed for local/test environments only.