Update the api key to reflect your account

mailgun.erl

%curl -s --user 'api:key-8av0ox9abrs2icvagny' \
%    https://api.mailgun.net/v2/bang.mailgun.org/messages \
%    -F from='Excited User <postmaster@bang.mailgun.org>' \
%    -F to=masquerade2ruslan@gmail.com \
%    -F subject='Hello' \
%    -F text='Testing some Mailgun awesomness!'

-module(mailgun).

-compile(export_all).

-define(ApiKey, "api:key-8av0ox9abrs2icvagny").

start()->
    ok=application:start(inets),
    ok=application:start(crypto),
    ok=application:start(asn1),
    ok=application:start(public_key),
    ok=application:start(ssl).

go()->
    fire(
        "Excited User <postmaster@bang.mailgun.org>", 
        "masquerade2ruslan@gmail.com", 
        "Hello", 
        "Testing some Mailgun awesomness!").

fire(From, To, Subject, Message)->
    
    Body = "from="++http_uri:encode(From)++
        "&to="++http_uri:encode(To)++
        "&subject="++http_uri:encode(Subject)++
        "&text="++http_uri:encode(Message),

    io:format("~n Sending ~p ~n", [Body]),

    Request = { 
        "https://api.mailgun.net/v2/bang.mailgun.org/messages", 
        [{ "Authorization", "Basic "++base64:encode_to_string(?ApiKey) }],
        "application/x-www-form-urlencoded",
        Body
    },

    case httpc:request(post, Request, [], [{body_format, string}] ) of
        {ok, {{_, 200, _}, _, Payload}} -> {ok, Payload};
        {ok, {{_, _, _}, _, Payload}}   -> {error, Payload};
        Error                           -> Error
    end.