Unfortunately, this one of these almost-done-but-never-released projects. I like it, it works in general but it needs some love to get the last TODOs done. It's open source, so feel free to get in touch with the code. If you're familiar with go, it's not that hard :)

smtp_exporter

smtp_exporter is a Prometheus Exporter for testing your outgoing mail server. It's internal design and usage is very similar to blackbox_exporter. There is currently only one Prober (smtp). Check the outstanding TODOs for more information. You can reload the configuration with a post request to /-/reload. There is also a history log like you know it from blackbox_exporter.

How to use it

kmille@linbox:smtp_exporter go run ./main.go ./history.go --web.listen-address="127.0.0.1:9125" --log.level=debug --config.file=smtp.yml

What you can test

Can I sent an authenticated mail (starttls)?

  smtp_starttls_authentication_ok:
    prober: smtp
    smtp:
      preferred_ip_protocol: ip4 
      tls: starttls
      auth:
           username: [email protected]
           password: mail-test-1password
      headers:
        from: [email protected]
        to: [email protected]

The output contains also information about the encryption (tls version, certificate validation, certificate expiration date). Debug Output

Can I sent an authenticated mail over ipv6 (tls)?

  smtp_tls_authentication_ok_ipv6:
    prober: smtp
    smtp:
      preferred_ip_protocol: ip6
      ip_protocol_fallback: false
      tls: tls
      ehlo: smtp01.wurbz.de
      mail_from: [email protected]
      mail_to: [email protected]
      auth:
           username: kmille
           password: ccc-password
      headers:
        from: [email protected]
        to: [email protected]
        subject: mail-monitoring
      body: This mail was sent over ipv6

You can specify ehlo, mail_from, mail_to, message headers. Debug Output

Is our mail delivered by the receiving mail server?

  smtp_starttls_imap_receiver:
    prober: smtp
    smtp:
      preferred_ip_protocol: ip4
      tls: starttls
      auth:
           username: [email protected]
           password: mail-test-1password
      headers:
        from: [email protected]
        to: [email protected]
      receiver: imap
      imap:
        tls: tls
        auth:
             username: [email protected]
             password: mail-test-1password
        mailbox: INBOX
        server: beeftraeger.wurbz.de
        port: 993

Every message the smtp_exporter sends contains a unique id in the subject. We can search for it in the mailbox using IMAP. Debug Output

Can I login with disabled credentials?

  smtp_tls_authentication_wrong:
    prober: smtp
    smtp:
      tls: tls
      auth:
        username: [email protected]
        password: thisisnotavalidpassword
      valid_status_codes:
      - 535

You can check for a list of SMTP status codes. Debug Output

Is authentication enabled without encryption?

  smtp_plain_authentication_not_available:
    prober: smtp
    smtp:
      auth:
        username: [email protected]
        password: thiswontwork
     valid_status_codes:
      - 530

tls can have the values no,starttls and tls. If no value is set no encryption is used. Debug Output

Can I forge email addresses (specify arbitrary from values) after authentication?

  smtp_starttls_auth_ok_forged_from:
    prober: smtp
    smtp:
      tls: starttls
      auth:
           username: [email protected]
           password: mail-test-1password
      headers:
        from: [email protected]
        to: [email protected]
        subject: test message
      body: I'm not authenticated to write emails as this user
      valid_status_codes:
      - 553

Debug Output

Do you accept mails without authentication (open relay?)

  smtp_starttls_open_relay:
    prober: smtp
    smtp:
      tls: starttls
      headers:
        from: [email protected]
        to: [email protected]
        body: This mail should be rejected because we are not authenticated.
      valid_status_codes:
      - 454

Debug Output

Do you reject mails if I'm not authorized to send mails as google.com?

  smtp_starttls_spam_message_rejected:
    prober: smtp
    smtp:
      headers:
        from: [email protected]
        to: [email protected]
      body: This mail should be rejected because the we are not authorized to send mail as google.com
      valid_status_codes:
      - 554

Debug Output