74 lines
1.4 KiB
Markdown
74 lines
1.4 KiB
Markdown
---
|
|
title: "e-mail"
|
|
tags: [ "data", "smtp" ]
|
|
---
|
|
|
|
This is bare-bones, original, primitive e-mail.
|
|
|
|
Install `opensmtpd` (or similar), then `ncat` or `nc` or `netcat` (this mysterious cat has many names).
|
|
|
|
Start the `opensmtpd` service, then use netcat to speak with the mail-daemon:
|
|
|
|
|
|
```
|
|
nc localhost 25
|
|
```
|
|
The computer should respond with code `220`, which means 'I am listening'.
|
|
|
|
> 220 hex ESMTP OpenSMTPD
|
|
|
|
```
|
|
HELO gmail.com
|
|
```
|
|
|
|
You say `HELO` and say where you are coming from.
|
|
|
|
|
|
The `smtpd` will not check, so I am going to lie to it.
|
|
Mail servers are easily impressed, so it will be pleased to meet you.
|
|
|
|
> 250 hex Hello gmail.com [::1], pleased to meet you
|
|
|
|
```
|
|
MAIL FROM: <admin@gmail.com>
|
|
```
|
|
|
|
All the mail commands start with 4 bytes, because it's easier for admins to program.
|
|
Tell the mail daemon who you are in this format.
|
|
|
|
> 250 2.0.0 Ok
|
|
|
|
Then tell it who you're sending to.
|
|
|
|
```
|
|
RCPT TO: <www@dmz.rs>
|
|
```
|
|
|
|
> 250 2.1.5 Destination address valid: Recipient ok
|
|
|
|
Finally, tell it that you want to send `DATA`.
|
|
|
|
```
|
|
DATA
|
|
```
|
|
|
|
> 354 Enter mail, end with "." on a line by itself
|
|
|
|
```
|
|
Subject: turn off server please
|
|
|
|
very urgent
|
|
.
|
|
```
|
|
|
|
> 250 2.0.0 73864a49 Message accepted for delivery
|
|
|
|
You will find the email under `/var/spool` or `/var/mail` or similar.
|
|
|
|
If unsure, just take a part of your email, like `FRAGMENT="turn off server please"`, then `grep` for it:
|
|
|
|
```bash
|
|
sudo grep -r $FRAGMENT /var/spool/*
|
|
```
|
|
|