64 Stars
Updated Last
10 Months Ago
Started In
October 2013


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A CURL based SMTP client with fairly low level API. It is useful for sending emails from within Julia code. Depends on LibCURL.jl.

The latest version of SMTPClient requires Julia 1.3 or higher. Versions of this package may be available for older Julia versions, but are not fully supported.



The LibCURL native library is automatically installed using Julia's artifact system.

Raw usage

using SMTPClient

opt = SendOptions(
  isSSL = true,
  username = "you@gmail.com",
  passwd = "yourgmailpassword")
#Provide the message body as RFC5322 within an IO
body = IOBuffer(
  "Date: Fri, 18 Oct 2013 21:44:29 +0100\r\n" *
  "From: You <you@gmail.com>\r\n" *
  "To: me@test.com\r\n" *
  "Subject: Julia Test\r\n" *
  "\r\n" *
  "Test Message\r\n")
url = "smtps://smtp.gmail.com:465"
rcpt = ["<me@test.com>", "<foo@test.com>"]
from = "<you@gmail.com>"
resp = send(url, rcpt, from, body, opt)
  • Sending from file IOStream is supported:

    body = open("/path/to/mail")

Example with HTML formatting

body = "Subject: A simple test\r\n"*
    "Mime-Version: 1.0;\r\n"*
    "Content-Type: text/html;\r\n"*
    "Content-Transfer-Encoding: 7bit;\r\n"*
    <h2>An important link to look at!</h2>
    Here's an <a href="https://github.com/aviks/SMTPClient.jl">important link</a>

Function to construct the IOBuffer body and for adding attachments

A new function get_body() is available to facilitate constructing the IOBuffer for the body of the message and for adding attachments.

The function takes four required arguments: the to and from email addresses, a subject string, and a msg string. The to argument is a vector of strings, containing one or more email addresses. The msg string can be a regular string with the contents of the message or a string in MIME format, following the RFC5322 specifications, and constructed as a plain text, html text or markdown text.

There are also the optional keyword arguments cc, replyto and attachments. The argument cc should be a vector of strings, containing one or more email addresses, while replyto is a string expected to contain a single argument, just like from. The attachments argument should be a list of filenames to be attached to the message.

The attachments are encoded using Base64.base64encode and included in the IOBuffer variable returned by the function. The function get_body() takes care of identifying which type of attachments are to be included (from the filename extensions) and to properly add them according to the MIME specifications.

In case an attachment is to be added, the msg argument must be formatted according to the MIME specifications. In order to help with that, another function, get_mime_msg(message), is provided, which takes the provided message and returns the message with the proper MIME specifications. By default, it assumes plain text with UTF-8 encoding, but plain text with different encodings or HTML text or Markdown text can also be given (see src/user.jl#L36 for more details on the implementation).

As for blind carbon copy (Bcc), it is implicitly handled by send(). Every recipient in send() which is not included in body is treated as a Bcc.

Here are a few examples:

Message with several types of recipients

using SMTPClient

opt = SendOptions(
  isSSL = true,
  username = "you@gmail.com",
  passwd = "yourgmailpassword"

url = "smtps://smtp.gmail.com:465"

subject = "SMPTClient.jl"
message = "Don't forget to check out SMTPClient.jl"

to = ["<foo@test.com>"]
cc = ["<bar@test.com>"]
bcc = ["<baz@test.com>"]
from = "You <you@test.com>"
replyto = "<you@gmail.com>"

body = get_body(to, from, subject, message; cc, replyto)

rcpt = vcat(to, cc, bcc)
resp = send(url, rcpt, from, body, opt)

Message with attachment

subject = "Julia logo"
message = "Check out this cool logo!"
attachments = ["julia_logo_color.png"]

mime_msg = get_mime_msg(message)

body = get_body(to, from, subject, mime_msg; attachments)

HTML message

Note that, by using get_mime_msg() with an HTML{String} message, the tags <html> and <body> should not be added.

subject = "A simple HTML test"
message = 
    html"""<h2>An important link to look at!</h2>
    Here's an <a href="https://github.com/aviks/SMTPClient.jl">important link</a>

mime_msg = get_mime_msg(message)

body = get_body(to, from, subject, mime_msg)
resp = send(server, rcpts, sender, body, opts)

Markdown message

using Markdown
subject = "The Julia Programming Language"
message = 
        """# The Julia Programming Language

        ## Julia in a Nutshell

        1. **Fast** - Julia was designed from the beginning for [high performance](https://docs.julialang.org/en/v1/manual/types/).
        1. **Dynamic** - Julia is [dynamically typed](https://docs.julialang.org/en/v1/manual/types/).
        1. **Reproducible** - recreate the same [Julia environment](https://julialang.github.io/Pkg.jl/v1/environments/) every time.
        1. **Composable** - Julia uses [multiple dispatch](https://docs.julialang.org/en/v1/manual/methods/) as a paradigm.
        1. **General** - One can build entire [Applications and Microservices](https://www.youtube.com/watch?v=uLhXgt_gKJc) in Julia.
        1. **Open source** - Available under the [MIT license](https://github.com/JuliaLang/julia/blob/master/LICENSE.md), with the [source code](https://github.com/JuliaLang/julia) on GitHub.

        It has *over 5,000* [Julia packages](https://juliahub.com/ui/Packages) and a *variety* of advanced ecosystems. Check out more on [the Julia Programing Language website](https://julialang.org).

mime_msg = get_mime_msg(message)

body = get_body(to, from, subject, mime_msg; cc, replyto)
resp = send(server, rcpts, sender, body, opts)

Previewing the generated message

You can preview your message by displaying the generated body, which is an IOBuffer.

For instance, you can view the raw message with println(String(take!(body))).

You can also save the message body to a .eml file for viewing it in a email viewer.

open("message.eml","w") do io
    println(io, String(take!(body)))

The last example on the previous section shows the following preview on Apple Mail:

Message on the Julia Programming Language

Gmail Notes

Due to the security policy of Gmail, you need to "allow less secure apps into your account":

The URL for gmail can be either smtps://smtp.gmail.com:465 or smtp://smtp.gmail.com:587. (Note the extra s in the former.) Both use SSL, and thus isSSL must be set to true in SendOptions. The latter starts the connection with plain text, and converts it to secured before sending any data using a protocol extension called STARTTLS. Gmail documentation suggests using this latter setup.


Since this package is a pretty thin wrapper around a low level network protocol, it helps to know the basics of SMTP while troubleshooting this package. Here is a quick overview of SMTP. In particular, please pay attention to the difference between the envelope headers and the message headers.

If you are having trouble with sending email, set verbose=true when creating the SendOptions object. Please always do this before submitting a bugreport to this project.

When sending email over SSL, certificate verification is performed, which requires the presence of a certificate authority bundle. This package uses the CA bundle from the Mozilla project. Currently there is no way to specify a private CA bundle. Modify the source if you need this.

Function Reference

send(url, to-addresses, from-address, message-body, options)

Send an email.

  • url should be of the form smtp://server:port or smtps://....
  • to-address is a vector of String.
  • from-address is a String. All addresses must be enclosed in angle brackets.
  • message-body must be a RFC5322 formatted message body provided via an IO.
  • options is an object of type SendOptions. It contains authentication information, as well as the option of whether the server requires TLS.
SendOptions(; isSSL = false, verbose = false, username = "", passwd = "")

Options are passed via the SendOptions constructor that takes keyword arguments. The defaults are shown above.

  • verbose: enable libcurl verbose mode or not.
  • If the username is blank, the passwd is not sent even if present.

Note that no keepalive is implemented. New connections to the SMTP server are created for each message.

Required Packages