Moxtools is a web app for inspecting mail infrastructure, serving as a showcase for reusing some of the Go packages of https://github.com/mjl-/mox, an email server. See https://pkg.go.dev/github.com/mjl-/mox#section-directories.

Moxtools runs at https://tools.xmox.nl, but you can easily run it locally without the rate limiting.

Similar functionality is also included in mox as subcommands (cli).

• Analyse SMTP server settings for a domain, looking up information in DNS (DNSSEC, MX, SPF, DMARC, TLSRPT, DANE, MTA-STS), and connecting to at most 2 SMTP servers.
• Verify the DKIM signatures in a message.
• Check SPF result for a given sending IP address for a given sender domain name.
• Lookup DKIM record given a selector and domain.

Download the latest version from https://beta.gobuilds.org/github.com/mjl-/moxtools

Or compile it yourself (with a recent Go toolchain):

go install github.com/mjl-/moxtools@latest

Now run:

./moxtools