swaldman / mailutil   0.0.3

Apache License 2.0 GitHub

Utilities for conveniently working with e-mail from Scala

Scala versions: 3.x



For now, this package just contains an API for super-simple sending by SMTP of plaintext and html-with-plaintext-alternative email.


Putting aside configuration, sending a plaintext e-mail is just...

//> using dep "com.mchange::mailutil:0.0.1"

import com.mchange.mailutil.Smtp

val contents = "This is some really exciting text here."
Smtp.sendSimplePlaintext( contents, subject = "So exciting!", from = "[email protected]", to = "[email protected]" )

That's it!

(But you really do have to have configured SMTP first.)

Flexible addressing

  • Wherever you can write an e-mail address like [email protected], you can also include a display name part, so You <[email protected]> would be fine, and many mail clients will display You as the to address.

  • Wherever you can write an e-mail address, you can write a comma-separated list of e-mail addresses, in any acceptable format. So, for example,

    Smtp.sendSimplePlaintext( contents, 
      subject = "So exciting!", 
      from = "[email protected]", 
      to = "Kitty <[email protected]>, Doggy<[email protected]>, [email protected]" 

    is fine.

  • In addition to from and to, you can provide cc, bcc, and replyTo

HTML mail

It's easy to send self-contained HTML mail.

"Self-contained" means no inclusion of, for example, images bundled into the mail. You can link to whatever you want, in a or img tags or whatever, although mail clients may be cautious about those references.

You will usually want to include CSS inline via a <style> ... </style> section under <head>.

It's best to include a plaintext alternative is required, although HTML-only mail is also supported.

//> using dep "com.mchange::mailutil:0.0.1"

import com.mchange.mailutil.Smtp

val plaintext = "This is some really exciting text here."
val html =
     |  <head>
     |    <title>So exciting!</title>
     |    <style>
     |      body {
     |        background-color: black;
     |        color: white;
     |      }
     |      h1 {
     |        color: cyan;
     |      }
     |    </style>
     |  </head>
     |  <body>
     |    <h1>So exciting!</h1>
     |    <p>This is some really exciting text here.</p>
     |  </body>
Smtp.sendSimpleHtmlPlaintextAlternative( html = html, plaintext = plaintext, subject = "So exciting!", from = "[email protected]", to = "[email protected]" )

Raw access to the jakarta-mail API

Once configured, you can use this library just for easy access to the raw jakarta-mail API:

import java.util.Date
import jakarta.mail.internet.MimeMessage
import com.mchange.mailutil.Smtp

def customSendMail()( using Smtp.Context ) =
  val ctx = summon[Smtp.Context]
  val msg = new MimeMessage( ctx.session ) // ctx.session is just a jakarta.mail.Session
  // do custom stuff
  msg.setSentDate(new Date())
  ctx.sendMessage(msg) // use this send message to inherit authentication / configuration


Via a properties file

The recommended configuration strategy is to define a Java-standard properties file, and specify its absolute location using either

  • the system property mail.smtp.properties; or
  • the environment variable SMTP_PROPERTIES

This approach keeps more sensitive information out of the environment or the command line, all of which can leak by, for example, use of the ps command.

Configuration properties include...

mail.smtp.password=???         # NOT a standard javax.mail property AFAIK
mail.smtp.starttls.enable=???  # Usually omit, we'll figure it out from the port provided
mail.smtp.debug=???            # Log extra debugging information

On the command line, or in the environment

If you prefer to live dangerously, any or all of these properties can also be provided directly as system properties, or via the following environment variables:

SMTP_START_TLS=??? # Same as SMTP_STARTTLS, just an alternative form

In code

You can also configure your SMTP provder directly in code:

val smtpAuth = Smtp.Auth("smtpuser", "supersecretpassword") // better to fetch the password from somewhere than hardcode it!

given Smtp.Context(
  host     = ???, // String
  port     = ???, // Int
  auth     = Some( smtpAuth ),
  startTls = ???, // boolean
  debug    = ??? // boolean
Smtp.sendSimplePlaintext( contents, subject = "So exciting!", from = "[email protected]", to = "[email protected]" )

Known shortcomings

You can drop into the Jakarta mail API and do anything.

But there is no clean API or conveniences for mail other than simple plaintext, self-contained HTML, or HTML / plaintext alternative. Attachments and embedded resources (like images) are not really supported.

It'd be nice to develop a general, clean Scala datastructure to model mail more generally, and make a convenience method which sends that datastructure.

Maybe someday.