yaroslaff / testmsg

Generate RFC-compliant e-mail messages for sending over SMTP. DKIM signed (optionally). Gmail.com and mail-tester.com are happy!

testmsg

Generate RFC822 compliant e-mail messages for tests and send it over SMTP.

While it's easy to send test messages like echo asdf | mail [e-mail] or via telnet mx.example.com 25 I need a tool which:

• Generates valid messages
• Messages does not looks spammy or very suspicious
• Easy to use and repeat test
• Ability to customize messages
• Work well with msmtp or other full-featured SMTP client (e.g. which can send over secure SMTP connection with authentication)
• Support DKIM signatures

Installation

pip3 install testmsg

or

pipx install testmsg

Usage examples

$ testmsg --to [e-mail]  --lorem 
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Subject: Sent with github.com/yaroslaff/testmsg
From: [e-mail]
To: [e-mail]

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempo=
r incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut al=
iquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore =
eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia des=
erunt mollit anim id est laborum.

Options

Sending message

To actually send message via SMTP server add --send localhost or (if you need really powerful SMTP client features) pipe to msmtp:

testmsg --lorem --to [e-mail] --from [e-mail] | msmtp --host mail.example.net -v --tls=on --tls-starttls=on --auth=on --user=[e-mail] --passwordeval "echo YourPass" -f [e-mail] [e-mail]

Customize message

Use --from, --to and --subject to override basic properties of message, use --add HEADER VALUE to add custom header(s).

Default message text is empty, use --text "blah blah blah" or --lorem or --msg PATH or --msg - .(to read from stdin). Add --time to add current time as an prefix to text.

Add attachments

Use --attachment (or --att) to add attachments: --att FILE1 FILE2 ...

Sign with DKIM

Generate DKIM RSA keys:

# generate private RSA key for DKIM
openssl genrsa -out example.com.pem 1024
# generate public key for DKIM
openssl rsa -in example.com.pem -out example.com.pub -pubout

Make DKIM DNS record with as SELECTOR._domainkey.example.com and verify it (here I decide to use selector mail):

$ host -t txt mail._domainkey.example.com
mail._domainkey.example.com.net descriptive text "v=DKIM1; h=sha256; k=rsa; p=MII...."

send DKIM signed message to gmail or mail-tester.com! Use --selector and --privkey arguments.

testmsg -f [e-mail] -t [e-mail] --lorem --selector mail --privkey example.com.pem -v --send localhost

Use with authentication and SSL/STARTTLS SMTP servers

To use authentication, use --user and --password (or --pass) parameters. Use --ssl to use SSL-capable SMTP server (port 465), or use --starttls to use STARTTLS SMTP command. If neither --ssl nor --starttls is given, message and authentication credentials are sent over plain unencrypted connection, which is highly insecure.

If --user is not given (but --password given), testmsg will use username same as from (--from / -f) address.

Example:

testmsg -v -f [e-mail] -t [e-mail] --lorem --pass "MyTestPass" --send mx.example.com --starttls

Use together with msmtp

Here we send with TLS and authentication (using msmtp). Username for authentication (--user) is same as FROM address. Testmsg generates valid message and msmtp sends it.

FROM=[e-mail]
TO=[e-mail]

testmsg -f $FROM -t $TO --lorem | msmtp -v --host smtp.office365.com --port 587 --user $FROM --passwordeval='echo MyTestPass' -f $FROM --tls=on --auth=on $TO