Lettersnail

Table of Contents

• What is lettersnail?
  • Motivation
• Quick Start
  • Building
  • Running
• Quick Start Walkthrough
• Folder structure
• Global Settings File .config/lettersnail.ini
  • Settings
• Message format
  • Configuration
  • Message Body
• Writing a New Message
• Command Line Options
  • next command
  • run command
  • create command
  • check command
  • debug command

lettersnail v0.0.1 — a simple email notification helper.

Important

This program is in development and might have some rough edges. The documentation on master should still accurately reflect the current state of the program.

What is lettersnail?

lettersnail is a “note to my future self” email notification tool. You write a simple text file, with some metadata, and it will, upon invocation, send a message when the time has come.

Example message

to: [email protected]
subject: Watch Halley's Comet
date: 2061-07-28

Greetings!

Go outside at night, if the curfew of the – highly welcomed — alien overlords
permits, and watch Halley's Comet.

Motivation

I needed a fairly simple tool to send some one-off reminders to myself, and possibly to others. Plus, I wanted the messages to live in my home directory, so I would not forget them if I move to another server. You could realize most of this with atd, but it is a bit clumsy if want to quickly write a message, plus I’d totally forget to copy /var/spool/at.

lettersnail is not meant to be a daemon. It should be executed regularly by a cron job or other method. For the date parameter it also supports having a specific time, which acts as a “not before” constraint. If you run your cron job often enough (for example: every five minutes) the message will, of course, be sent very close to the given time.

Quick Start

Building

In order to check out and build the project in its own directory in /tmp, write the following:

cd $(mktemp -d)
git clone http://github.com/githubert/lettersnail
go build

Running

Create .config/lettersnail.ini:

[default]
server = smtp.example.com
user = me
password = aengeequ6xeiseoY
from = [email protected]

Create a new message:

lettersnail create --to [email protected]

Add a cron job:

0 6 * * * /path/to/lettersnail run

List messages due in the next days:

lettersnail next

Run manually:

lettersnail run

Quick Start Walkthrough

Create a file .config/lettersnail.ini and provide a server, credentials and a from address:

[default]
server = smtp.example.com
user = me
password = aengeequ6xeiseoY
from = [email protected]

Note	port defaults to 587. If it doesn’t work, try setting port to 25.

Now ready some message to yourself:

lettersnail create --to [email protected]

This will open a new file using the editor set in the VISUAL environment variable, or if no editor is set, it will default to vi.

Fill in date in the format YYYY-mm-dd (for example date: 2016-01-01) and add a meaningful subject. Add a blank line between the configuration in the header and your message’s body.

Save and exit the editor. lettersnail will ask you what to do. Press ENTER to save the message to the lettersnail/todo folder.

If you set date to today’s date you can test if everything works. First check if everything is okay by running lettersnail check, if it reports no errors, you can see with lettersnail next if the message is scheduled for being sent out in the next seven days.

Finally, if you type lettersnail run, it will deliver all messages that were due.

As lettersnail is not a daemon, you should run it daily by adding it as a cron job.

Type crontab -e and add a entry to run the command every day at 6 in the morning:

0 6 * * * /path/to/lettersnail run

Folder structure

The default working directory is lettersnail, located in the user’s home directory. There are several folders created beneath it, when the program is invoked.

lettersnail/
  todo/
  done/
  errors/
  drafts/

todo/ is the message queue. All .msg files in that folder are considered when running lettersnail run.

done/ contains all messages that were successfully delivered. For every message there is also a corresponding .log file.

errors/ contains all messages that could not be delivered. For every message there is also a corresponding .log file.

drafts/ contains messages that can be used with lettersnail create --draft FILENAME. Additionally, messages in this folder will also be checked with lettersnail check.

Global Settings File .config/lettersnail.ini

Global settings can be put into the optional file .config/lettersnail.ini.

All global settings can also be overridden on the command line.

.config/lettersnail.ini is a simple ini-style settings file with a default section, plus optional sections for every command, in order to overrule the settings in the default section.

Example file

[default]
workdir = ~/lettersnail
server = smtp.example.com
port = 587
from = [email protected]

[run]
bcc = [email protected]

Settings

Note	Empty values are valid and mean that a setting has been un-set.

Global and Command Line

workdir

The working directory, defaults to ~/lettersnail.

server

Address of the SMTP server. Defaults to localhost.

port

Port of the SMTP server. Defaults to the SMTP submission port 587.

not-before

Do not sent messages before the specified time. (00:00 until not-before)

not-after

Do not sent messages after the specified time. (not-after until 23:59)

TODO: not-after / not-before warrant some better explanation

Priority of these is as follows command line > global.

Global, Command Line and as Configuration

These parameters are valid everywhere and may also be included in the configuration part of a message.

Note	date is not allowed anywhere except in the message configuration.

from

from as in Configuration

to

to as in Configuration

cc

cc as in Configuration

bcc

bcc as in Configuration

subject

subject as in Configuration

reply-to

reply-to as in Configuration

Priority of these is as follows configuration > command line > global.

Message format

Messages consist of two parts separated by a single empty line. The first part is the configuration and the second part is the actual message.

Example message

to: [email protected]
from: [email protected]
cc: [email protected]
subject: Unfreeze Clemens
date: 2134-01-01

Dear Cryogenics Department,

please unfreeze Clemens, as he wanted to watch this year's close pass of
Halley's Comet. This one is going to have an apparent magnitude of -2.0 — it's
gonna be fun, so feel free to join him!

Configuration

The following parameters are permitted, everything else is going to be ignored.

Required parameters

Note	Except for date, other required parameters may be specified outside the message configuration, either on the command line or in the ini-file.

date

The "not before" date. This may either be a simple date in the format YYYY-mm-dd, which will be interpreted as YYYY-mm-dd 00:00, or a date with a time in the form of YYYY-mm-dd HH:MM.

to

A single address to where the message will be sent. It may either be a simple email address such as [email protected] or an address including a name such as Foo bar <[email protected]>.

subject

A short subject.

from

Same format as to.

Optional parameters

cc

Same format as to, but multiple comma-separated entries are allowed, works like Cc in email.

bcc

Same format as to, but multiple comma-separated entries are allowed, works like Bcc in email.

reply-to

Same format as to, works like Reply-To in email.

Message Body

Simple, plain text. It is assumed to be in UTF-8, though.

Writing a New Message

Either edit a file, directly in lettersnail/todo, or use the command line tool to initialize an empty message and start your favourite editor. The file name must end in .msg, otherwise it will be ignored.

Using the command line tool

$ lettersnail create --to "[email protected]"

Command Line Options

Use --help after any command to get the full help message shown.

link:lettersnail.go[role=include]

next command

link:cmd/next.go[role=include]

This will show which messages are going to be sent within the next 7 days. Use the --days parameter to change how many days in advance are processed. If you use the --all parameter, all pending messages will be listed. The format is simply date subject (filename).

$ lettersnail next --all
Showing all messages.

2061-07-28 00:00  Watch Halley's Comet (halley.msg)
2134-01-01 00:00  Unfreeze Clemens (unfreeze.msg)

run command

link:cmd/run.go[role=include]

This will send out all pending messages. There will be no output, unless there were errors. Any message that could not be sent will be moved to the errors folder, and a corresponding .log-file will be created with all available information; additionally, the program will start to complain at every invocation that there were messages with errors. Messages that were delivered successfully are moved to the done folder and a corresponding .log-file is created there, too.

create command

link:cmd/create.go[role=include]

The create command will assist you in creating a new message. It will open a new file for you, filled in with any parameters you provided on the command line. If you provide a file name through the --draft parameter, it will create a new file based on the given file name in the drafts folder.

lettersnail create --to [email protected] --subject "Something"

It will use the editor configured in $VISUAL or $EDITOR or vi, if the former are empty.

date will be set to tomorrow’s date.

1 to: [email protected]
2 subject: Something
3 date: 2016-01-01
4
5 Add message to the world of tomorrow here.
~
~
~
~
 INSERT >> [No Name][+]               <<<
-- INSERT --

After editing it will ask you if you want to add the message to the todo folder.

Save message? ([(y)es], (r)enamed, (d)raft, (n)o):

Answering n or no will discard the message, answering d or draft will add it to the drafts folder. If you type y, yes, or simply hit ENTER it will be added to the todo folder. If you want to save the message under a different name, but still into the todo folder, you may anwer with r or renamed — the program will then prompt you for a new name, without the .msg extension.

check command

link:cmd/check.go[role=include]

The check command will check all messages in the todo and drafts folder and report any messages that can’t be processed. Optionally a file name can be provided to check only the given file. It will exit with a code of 0 if no errors were found, otherwise with a code of 1.

Note	--silent will not suppress output of errors, such as problems loading a file.

$ lettersnail check

in drafts:
 foo.msg:
    missing the 'to' parameter
    missing the 'subject' parameter

in todo:
 bar.msg:
    'date' parameter is invalid

debug command

link:cmd/debug.go[role=include]

The debug command will print out the effective configuration for a message, plus the email message. This shows all settings as they are seen at that point. Note that this also shows settings — such as workdir and config — that cannot be overridden by the message. Please note that for the email message there are several places, such as the Message-Id, that vary from invocation to invocation as they are randomly generated.

$ lettersnail debug lettersnail/todo/2061.msg
Configuration
-------------
config: /home/me/.config/config.ini
date: 2061-07-28
days: 7
from: [email protected]
not-after: 23:59
not-before: 00:00
port: 578
server: smtp.example.com
subject: Watch Halley's Comet
to: [email protected]
workdir: /home/me/lettersnail

Email message
-------------
Content-Type: multipart/mixed;
 boundary=8bb4fce665d20481a3b832ef74a12123edadb7b1bc4d5b505c93e9fbd9e2
To: <[email protected]>
Subject: Watch Halley's Comet
Message-Id: <[email protected]>
From: [email protected]
Date: Fri, 03 Jun 2016 17:51:49 +0200
Mime-Version: 1.0

--8bb4fce665d20481a3b832ef74a12123edadb7b1bc4d5b505c93e9fbd9e2
Content-Type: multipart/alternative;
 boundary=70b52bfb5fa8b90ebe2b3b9373f62436d412ae3e59bbfa20685dbc1bd6bc

--70b52bfb5fa8b90ebe2b3b9373f62436d412ae3e59bbfa20685dbc1bd6bc
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

Greetings!

Go outside at night, if the curfew of the – highly welcomed — alien overlords
permits, and watch Halley's Comet.
--70b52bfb5fa8b90ebe2b3b9373f62436d412ae3e59bbfa20685dbc1bd6bc--

--8bb4fce665d20481a3b832ef74a12123edadb7b1bc4d5b505c93e9fbd9e2--