2019-08-28 23:23:11 +00:00
|
|
|
---
|
|
|
|
title: How to Send Email with Nim
|
|
|
|
date: 2019-08-28
|
2019-09-12 22:49:03 +00:00
|
|
|
series: howto
|
|
|
|
tags:
|
|
|
|
- nim
|
|
|
|
- email
|
2019-08-28 23:23:11 +00:00
|
|
|
---
|
|
|
|
|
|
|
|
# How to Send Email with Nim
|
|
|
|
|
|
|
|
Nim offers an [smtp][nimsmtp] module, but it is a bit annoying to use out of the
|
|
|
|
box. This blogpost hopes to be a mini-tutorial on the basics of how to use the
|
|
|
|
smtp library and give developers best practices for handling outgoing email in
|
|
|
|
ways that Google or iCloud will accept.
|
|
|
|
|
|
|
|
## SMTP in a Nutshell
|
|
|
|
|
|
|
|
[SMTP][SMTPrfc], or the Simple Mail Transfer Protocol is the backbone of how
|
|
|
|
email works. It's a very simple line-based protocol, and there are wrappers for
|
|
|
|
it in almost every programming language. Usage is pretty simple:
|
|
|
|
|
|
|
|
- The client connects to the server
|
|
|
|
- The client authenticates itself with the server
|
|
|
|
- The client signals that it would like to create an outgoing message to the server
|
|
|
|
- The client sends the raw contents of the message to the server
|
|
|
|
- The client ends the message
|
|
|
|
- The client disconnects
|
|
|
|
|
|
|
|
Unfortunately, the devil is truly in the details here. There are a few things
|
|
|
|
that _absolutely must_ be present in your emails in order for services like
|
|
|
|
GMail to accept them. They are:
|
|
|
|
|
|
|
|
- The `From` header specifying where the message was sent from
|
|
|
|
- The Mime-Version that your code is using (if you aren't sure, put `1.0` here)
|
|
|
|
- The Content-Type that your code is sending to users (probably `text/plain`)
|
|
|
|
|
|
|
|
For a more complete example, let's create a `Mailer` type and a constructor:
|
|
|
|
|
|
|
|
```nim
|
|
|
|
# mailer.nim
|
|
|
|
import asyncdispatch, logging, smtp, strformat, strutils
|
|
|
|
|
|
|
|
type Mailer* = object
|
|
|
|
address: string
|
|
|
|
port: Port
|
|
|
|
myAddress: string
|
|
|
|
myName: string
|
|
|
|
username: string
|
|
|
|
password: string
|
|
|
|
|
|
|
|
proc newMailer*(address, port, myAddress, myName, username, password: string): Mailer =
|
|
|
|
result = Mailer(
|
|
|
|
address: address,
|
|
|
|
port: port.parseInt.Port,
|
|
|
|
myAddress: myAddress,
|
|
|
|
myName: myName,
|
|
|
|
username: username,
|
|
|
|
password: password,
|
|
|
|
)
|
|
|
|
```
|
|
|
|
|
|
|
|
And let's write a `mail` method to send out email:
|
|
|
|
|
|
|
|
```nim
|
|
|
|
proc mail(m: Mailer, to, toName, subject, body: string) {.async.} =
|
|
|
|
let
|
|
|
|
toList = @[fmt"{toName} <{to}>"]
|
|
|
|
msg = createMessage(subject, body, toList, @[], [
|
|
|
|
("From", fmt"{m.myName} <{m.myAddress}"),
|
|
|
|
("MIME-Version", "1.0"),
|
|
|
|
("Content-Type", "text/plain"),
|
|
|
|
])
|
|
|
|
|
|
|
|
var client = newAsyncSmtp(useSsl = true)
|
|
|
|
await client.connect(m.address, m.port)
|
|
|
|
await client.auth(m.username, m.password)
|
|
|
|
await client.sendMail(m.myAddress, toList, $msg)
|
|
|
|
info "sent email to: ", to, " about: ", subject
|
|
|
|
await client.close()
|
|
|
|
```
|
|
|
|
|
|
|
|
Breaking this down, you can clearly see the parts of the SMTP connection as I
|
|
|
|
laid out before. The `Mailer` creates a new transient SMTP connection,
|
|
|
|
authenticates with the remote server, sends the properly formatted email to
|
|
|
|
the server and then closes the connection cleanly.
|
|
|
|
|
|
|
|
If you want to test this code, I suggest testing it with a freely available
|
|
|
|
email provider that offers TLS/SSL-encrypted SMTP support. This also means that
|
|
|
|
you need to compile this code with `--define: ssl`, so create `config.nims` and
|
|
|
|
add the following:
|
|
|
|
|
|
|
|
```nimscript
|
|
|
|
--define: ssl
|
|
|
|
```
|
|
|
|
|
|
|
|
Here's a little wrapper using [cligen][cligen]:
|
|
|
|
|
|
|
|
```nim
|
|
|
|
when isMailModule:
|
|
|
|
import cligen, os
|
|
|
|
|
|
|
|
let
|
|
|
|
smtpAddress = getEnv("SMTP_ADDRESS")
|
|
|
|
smtpPort = getEnv("SMTP_PORT")
|
|
|
|
smtpMyAddress = getEnv("SMTP_MY_ADDRESS")
|
|
|
|
smtpMyName = getEnv("SMTP_MY_NAME")
|
|
|
|
smtpUsername = getEnv("SMTP_USERNAME")
|
|
|
|
smtpPassword = getEnv("SMTP_PASSWORD")
|
|
|
|
|
|
|
|
proc sendAnEmail(to, toName, subject, body: string) =
|
|
|
|
let m = newMailer(smtpAddress, smtpPort, smtpMyAddress, smtpMyName, smtpUsername, smtpPassword)
|
|
|
|
waitFor m.mail(to, toName, subject, body)
|
|
|
|
|
|
|
|
dispatch(sendAnEmail)
|
|
|
|
```
|
|
|
|
|
|
|
|
Usage is simple:
|
|
|
|
|
|
|
|
```console
|
|
|
|
$ nim c -r mailer.nim --help
|
|
|
|
Usage:
|
|
|
|
sendAnEmail [required&optional-params]
|
|
|
|
Options(opt-arg sep :|=|spc):
|
|
|
|
-h, --help print this cligen-erated help
|
|
|
|
--help-syntax advanced: prepend,plurals,..
|
|
|
|
-t=, --to= string REQUIRED set to
|
|
|
|
--toName= string REQUIRED set toName
|
|
|
|
-s=, --subject= string REQUIRED set subject
|
|
|
|
-b=, --body= string REQUIRED set body
|
|
|
|
```
|
|
|
|
|
|
|
|
I hope this helps, this module is going to be used in my future post on how to
|
|
|
|
create an application using Nim's [Jester][jester] framework.
|
|
|
|
|
|
|
|
[nimsmtp]: https://nim-lang.org/docs/smtp.html
|
|
|
|
[SMTPrfc]: https://tools.ietf.org/html/rfc5321
|
|
|
|
[jester]: https://github.com/dom96/jester
|
|
|
|
[cligen]: https://github.com/c-blake/cligen
|