swaks

Send test email to a server

$ swaks -t [user@example.com] -s [mail-server.example.com]

$ swaks -t [user@example.com] -f [me@example.com] -a CRAM-MD5 -au [me@example.com]

$ swaks -t [user@example.com] --header-X-Test "[test_value]"

$ swaks -t [user@example.com] --attach [path/to/file]

$ swaks -t [user@example.com] --socket [/var/lda.sock] --protocol LMTP

$ swaks -t [user@example.com] -s [server] --tls

$ swaks -t [user@example.com] -n

swaks [OPTIONS]

swaks (Swiss Army Knife SMTP) is a comprehensive SMTP testing tool for diagnosing mail server configurations, testing authentication, and verifying email delivery. It supports SMTP, ESMTP, and LMTP protocols over various transports including TCP sockets, UNIX sockets, and TLS connections.
The tool is invaluable for testing spam filters (using GTUBE), virus scanners (using EICAR), authentication mechanisms, and TLS configurations. It provides detailed transaction logging for troubleshooting.

-t, --to address

Recipient email address

Sender email address

SMTP server hostname or IP

SMTP port (default: 25)

Authentication type (PLAIN, LOGIN, CRAM-MD5, etc.)

Authentication username

Authentication password

Use STARTTLS

Use implicit TLS (SMTPS)

Connect via UNIX domain socket

Protocol: SMTP, ESMTP, LMTP

Attach file to message

Use file as message body

Add custom header

Don't show DATA portion

Minimize output

Connection timeout

Requires Perl. Passwords on command line are visible in process listings; use config files for sensitive data. Some authentication methods require additional Perl modules. Test emails may trigger spam filters.

swaks was created by John Jetmore and has been actively maintained since the early 2000s. It has become a standard tool for mail server administrators and is available in most Linux distribution repositories. The tool is written in Perl and released under GPLv2.

sendmail(8), postfix(1), openssl(1), telnet(1)