mxcheck is an info scanner for e-mail servers.

It checks

• DNS records: A, MX, PTR, SPF, MTA-STS, DKIM, DMARC (fully parsed), TLSRPT, BIMI
• AS Number and AS Country
• the support of StartTLS and the certificate
• TLS certificate details on port 465: expiry date, Subject CN, Issuer CN, SANs
• open ports: 25, 465, 587
• if the service is listed by blacklists
• if it leaks information by server string and VRFY command
• if the e-mail server is vulnerable to SMTPSmuggling
• and if the server is an open relay

You can set mailFrom, mailTo, the DNS server, DKIM selector and output a report in tsv format.

-b, --blacklist          Check if the service is on blacklists
-d, --dnsserver string   The dns server to be requested (default "8.8.8.8")
-g, --smuggle            Scan for SMTPSmuggling vulnerability
-p, --disable-port-scan  Disable SMTP port scan
-f, --mailfrom string    Set the mailFrom address (default "info@foo.wtf")
-t, --mailto string      Set the mailTo address (default "info@baz.wtf")
-n, --no-prompt          Answer yes to all questions
-s, --service string     The service host to check (mandatory flag)
-S, --dkim-selector      The DKIM selector. If set a dkim check is performed on the provided service domain
-v, --version            Version and license
-u, --updatecheck        Check if a new version of mxcheck is available
-w, --write-tsv          Write tsv formated report to file

Version

v1.8.0

Installation

go install github.com/steffenfritz/mxcheck@v1.8.0

or

download a pre-compiled binary.

or

use Kali Linux repositories

Usage Example

./mxcheck -s 2600.com
./mxcheck -s 2600.com -v
./mxcheck -s 2600.com -d 8.8.8.8
./mxcheck -s 2600.com -n -f info@baz.com -t boss@foo.org -w -S default
./mxcheck -s 2600.com -n -f info@baz.com -t boss@foo.org -w -S default -b -g

Check for authentication

There is no check whether the server needs authentication. However, you can do two runs:

The first one uses a from and to address outside the mail server's scope, e.g.:

./mxcheck -s example.com -f info@baz.com -t boss@foo.org

The second one uses a from and a to address from the mail server's scope, e.g.:

./mxcheck -s example.com -f info@example.com -t boss@example.com

If the first one returns Server is not an open relay and the second one returns Server is probably an open relay the server is not an open relay, but you can send mails from local to local addresses without authentication.

Documentation and contact

mxcheck has a man page :)

Furthermore, you can find a documentation and contact information here: https://mxcheck.fritz.wtf

The logo was created by Alex/Lignum5. Thanks, mate :)