Link: https://github.com/ehloonion/onionmx

Mail servers no longer simply accept RFC-compliant email. Thanks to Google, Microsoft, and Spamhaus, when you are forced to send an email you are forced through a series of arbitrary hurdles and obsticles imposed by the recipient. Every hurdle is an attack on your personal freedom and autonomy. It’s an attack on your control over what info you disclose to who.

This guide is for a few (perhaps rare) circumstances:

• You are expected to send an email to a person or org, e.g. per a legal obligation, but you would rather not give in to email-pushers who at the same time impose hurdles on email acceptance (network non-neutrality).
• You have missed a deadline to send an email and need a good excuse for missing the deadline.
• You are going to send a snail mail to an org for whatever reason. If you are taking the time to send them a letter anyway, might as well nitpick their mail server and add a log showing a refusal by their overly defensive mail server, just to drive the point that email cannot be relied on under their configuration. Gov agencies and various orgs are unplugging their fax machines with reckless disregard because they do not know their email shit stinks.

Email has become so enshitified by corporate assholes (Google and Microsoft) that it’s generally easy to be refused and to collect a server log showing a denial. You simply stand up a mail server on a residential network and configure it to directly connect to the recipient’s mail server. This is the default config, in fact.

Some uncommon mail servers still accept connections from residential IP spaces, so merely running your own server does not cover all bases. You can go a step further and configure the mail server to connect over Tor. It still does not guarantee refusal but it substantially increases the chances of refusal.

The onionmx project is stale but still relevant. A failure log looks like this:

to=<foo@some.org>, relay=none, delay=126, delays=0.09/0.11/126/0, dsn=4.4.1, status=deferred (connect to some.org[1.1.99.99]:25: Connection refused)

If you don’t want to risk sending a bluff email that risks getting accepted, simply do an MX lookup using dig:

dig @"${dnssvr}" -t mx -q "$domain" +noclass +nocomments +nostats +short +tcp +nosearch

then telnet to port 25 of the MX server. First try direct from your residential IP. If you can connect then try the same again over Tor. This will give a quick idea of whether the connection is allowed.

The reason email has become an exclusive and unreliable piece of shit is ultimately because there are too many conformists who are okay with Microsoft and Google controlling how email works -- denying RFC-compliant transactions to force more senders into corporate dependency. Push back is needed. Anyone who objects to MS and Google dictating terms has a duty of civil disobedience.