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Internet email library for Clojure

postal is a library for constructing and sending RFC822-compliant Internet email messages. It wraps the JavaMail package for message and SMTP support. It supports sendmail natively. Supports STARTTLS & SSL.


  • Anything that can run Java should work
  • sendmail support likely requires *nix, but msmtp, et al., are worthy substitutes
  • Untested on Windows


  • JavaMail 1.4.2 (in lib/ after build)


Served by Clojars. In your project.clj:

[com.draines/postal "1.7.1"]

Likewise substitute any tag, like 1.6.0 etc.


At a bare minimum, provide a map with :from and :to (and you'll probably also be wanting :subject and :body, though they're technically optional). This will locally inject the message into sendmail.

user> (in-ns 'postal.core)
#<Namespace postal.core>
postal.core> (send-message {:from ""
                            :to ["" ""]
                            :cc ""
                            :subject "Hi!"
                            :body "Test."})
{:code 0, :error :SUCCESS, :message "message sent"}

To use SMTP, add metadata with a :host key.

postal.core> (send-message ^{:host ""}
                           {:from ""
                            :to ""
                            :subject "Hi!"
                            :body "Test."})
{:code 0, :error :SUCCESS, :message "message sent"}

Authenticate to SMTP server with :user and :pass.

postal.core> (send-message ^{:host ""
                             :user "jsmith"
                             :pass "sekrat!!1"}
                           {:from ""
                            :to ""
                            :subject "Hi!"
                            :body "Test."})
{:code 0, :error :SUCCESS, :message "message sent"}

You probably do not want to do this in the clear, so add :ssl to get an encrypted connection. This will default to port 465 if you don't specify one.

If your destination supports TLS instead, you can use :tls. This will default to port 25, however, so if you need a different one make sure you supply :port. (It's common for ISPs to block outgoing port 25 to relays that aren't theirs. Gmail supports SSL & TLS but it's easiest to just use SSL since you'll likely need port 465 anyway.)

postal.core> (send-message ^{:host ""
                             :user "jsmith"
                             :pass "sekrat!!1"
                             :ssl :yes!!!11}
                           {:from ""
                            :to ""
                            :subject "Hi!"
                            :body "Test."})
{:code 0, :error :SUCCESS, :message "message sent"}

Attachments and multipart messages can be added as sequences of maps:

postal.core> (send-message ^{:host ""}
                           {:from ""
                            :to ""
                            :subject "Hi!"
                            :body [{:type "text/html"
                                    :content "<b>Test!</b>"}
                                   ;;;; supports both dispositions:
                                   {:type :attachment
                                    :content ( "/tmp/foo.txt")}
                                   {:type :inline
                                    :content ( "/tmp/a.pdf")
                                    :content-type "application/pdf"}]})
{:code 0, :error :SUCCESS, :message "message sent"}

If your attachment has a content-type that is not recognized by JavaMail, e.g., .pdf or .doc, you can set :content-type.

If you want another multipart type than "mixed", you can specify it as a keyword as the first value in the map sequence. That way you can for example create an HTML-Email that displays a text message as fallback in email clients that do not support (or suppress) HTML-mails:

postal.core> (send-message ^{:host "localhost"
                             :port 2500
                             :user "user@localhost"
                             :pass "somePassword"}
                       {:from ""
                        :to ""
                        :subject "multipart/alternative test"
                        :body [:alternative
                               {:type "text/plain"
                                :content "This is a test."}
                               {:type "text/html"
                                :content "<html><head> </head><body>
                                <h1>Heading 1</h1><p>This is a test.</p>

You can stress-test a server by:

postal.core> (stress ^{:host "localhost"
                       :num     1000
                       :delay   250   ;; msecs
                       :threads 5     ;; concurrent connections}
                     {:from "foo@lolz.dom"
                      :to "bar@lolz.dom"})
sent 1000 msgs to localhost:25

Since Amazon SES uses authenticated SMTP, postal can use it. Just make sure you use a verified address and your SMTP credentials (visit the AWS Console to set those up). Also, if you're just sandboxing, you can only send to a verified address as well. Example:

postal.core> (send-message ^{:user "AKIAIDTP........" :pass "AikCFhx1P......."
                             :host ""
                             :port 587}
               {:from "" :to ""
                :subject "Test from Amazon SES" :body "Test!!!11"})
{:error :SUCCESS, :code 0, :message "messages sent"}


% lein deps && lein jar


André Branco
Joe Gallo
Christoph Henkelmann
Gerrit Hentschel
Jeff Palmucci
Paul Stadig
Sam Ritchie


Postal is (c) 2009-2011 Andrew A. Raines and released under the MIT license.

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