E-mail handling
Any Zotonic system is capable of sending and receiving e-mail messages over SMTP.
Zotonic implements a mailing system for sending text and HTML messages to one or more recipients.
Out of the box, e-mail sending should “just work”.
Site-specific configuration
| Module | Key | Value |
|---|---|---|
| site | email_from | Set this to the from-address you want to e-mail to appear from, e.g. something like noreply@yoursite.com. |
| site | email_override | If set, all e-mail messages that get sent from Zotonic will arrive at this address. Useful if you are testing but don’t want to confuse other people with your test e-mails. |
| site | smtphost | The hostname where you want messages to appear from. Mostly used for bounce message handling and the EHLO handshake. Defaults to the site’s hostname, but can be overriden |
| site | admin_email | E-mail address of the admin user, the address where admin log/debug messages get sent to when using z_email:send_admin/3. |
| site | bounce_email_override | E-mail address where bounces are sent to. Normally a special bounce address is generated. See also the discussion about smtp_bounce_email_override below. |
| site | email_images_noembed | Images in emails are inlined if they are smaller than 1MB. Setting this config disables the inlining of images, the html image tags will be unchanged. |
Zotonic-wide configuration
The file ~/.config/zotonic/1/zotonic.config (on macOS ~/Library/Application Support/zotonic/config/1/zotonic.config) can be configured to hold any of the configuration options below. They are in effect for every site running in the Zotonic instance.
Zotonic-wide configuration for sending email
| Key | Description |
|---|---|
| smtp_relay | Whether or not to use a SMTP relay host. Boolean value, defaults to false. |
| smtp_host | The hostname for the SMTP relay host, only needed if smtp_relay is enabled. |
| smtp_ssl | Whether or not to use SSL/TLS on the relay host, only needed if smtp_relay is enabled. |
| smtp_username | The username for the relay host, only needed if smtp_relay is enabled. |
| smtp_password | The password for the relay host, only needed if smtp_relay is enabled. |
| smtp_no_mx_lookups | Set to true to not do a MX lookup before sending mail. (default: false) |
| smtp_verp_as_from | Use the “from” address as VERP for bounce handling (default: false) |
| smtp_bcc | Optionally send a BCC of every sent to this address |
| email_override | A global e-mail override. The override logic first checks the site override, and then the global override address. Useful for testing and development. |
| smtp_bounce_domain | Which domain to use for bounce VERP messages. Defaults to the smtp domain of the site sending the email. |
| smtp_bounce_email_override | The email address for bounce handling. Only use if all else fails (see the paragraphs after the next one). |
| smtp_plaintext_fallback | Retry using plain-text delivery if the TLS delivery failed with a timeout or closed error. Useful for servers with self-signed certificates or other TLS problems. (default: true) |
| smtp_is_blackhole | Drop all outgoing email, the mail is still logged. Good for testing large mailings. |
Zotonic-wide settings for receiving email
To receive email the SMTP server has to listen on the correct IP address and port. Spam filtering is done by checking DNSBL (DNS Block List) servers and optionally using Spamassassin.
| Key | Description |
|---|---|
| smtp_listen_domain | The domain announced in the HELO |
| smtp_listen_ip | IP address to listen on for incoming SMTP connections. Defaults to "127.0.0.1" Set to none to disable the smtp server. |
| smtp_listen_port | IP address to listen on for incoming SMTP connections. Defaults to 2525. Set to none to disable the smtp server. |
| smtp_dnsbl | List for the DNS block lists used for checking incoming email connections. Defaults to ["zen.spamhaus.org", "dnsbl.sorbs.net"] |
| smtp_dnswl | List for the DNS white lists used for checking incoming email connections. Defaults to ["list.dnswl.org", "swl.spamhaus.org"] |
| smtp_spamd_ip | Optional IP address for a spamassassin host |
| smtp_spamd_port | Optional port number for a spamassassin host |
The sender’s domain
Recipients of e-mail want a valid sender’s address on the envelope. This section describes how to set your e-mail bounce/sender domain and fixing domain errors when sending e-mail.
You have to think of e-mail as normal snail mail. There is a message and an envelope.
The email_from is the address that is written on the message. It could be anything, and is generally not used when delivering your mail. Just like with snail mail, the postman only looks on the envelope, not on the message.
The address on the envelope is the most important address. It is where your e-mail is returned to when the message can‘t be delivered (so called bounces). Often it is also checked for validity when the e-mail is delivered at a SMTP server.
You need a valid domain for this envelope sender address. The part before the @ is generated by Zotonic and is used for identifying the original message and recipient when the message bounces.
If the generated part is not acceptable then you can force an envelope address by setting the smtp_bounce_email_override option. Setting the bounce/envelop address manually disables Zotonic’s build-in handling of bounces that happen after the e-mail was accepted for delivery by the remote SMTP host.
The bounce e-mail address can also be set on a per-site basis using the site.bounce_email_override configuration. See the site specific settings table above.
How does Zotonic know the domain?
It checks in order:
- site’s config:
bounce_email_override(you can also set this with the admin config as site.bounce_email_override) - global
zotonic.config:smtp_bounce_domainsetting - site’s config:
smtphost - site’s config:
hostname
Any bounce_email_override configuration must be a complete email address. For example: bounces@example.org
If no bounce_email_override is used then the part before the @ is generated by Zotonic itself, for administration and detection of bounces. A typical sender address on the envelope looks like: noreply+mlcm6godbz2cchtgdvom@example.org
Sending E-mail
Once configured, you can use the following Erlang commands to send e-mail from Zotonic code:
| Command | Explanation |
|---|---|
z_email:send_admin/3 |
Sends a quick e-mail to the site administrator. Handy to notice the site admin that something is wrong, a job has finished, etc… The e-mail that is used is the admin_email address that is specified in the site’s config file. |
z_email:send/4 |
Sends a text message with a subject to a specified recipient. |
z_email:send_render/4 |
Renders a template and sends it as a HTML message to a specified recipient. |
z_email:send/2 |
Sends an email defined by a #email{} record. |
Send e-mail from a template
First, create a template for the e-mail. Just like normal templates, it can contain variables. The <title> tag becomes the e-mail’s subject:
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<title>An e-mail from {{ sender_name }} at {{ m.site.title }}</title>
</head>
<body>
Hello {{ id.name_first }},
Hope you’re doing fine!
Cheers,
{{ sender_name }}
</body>
</html>
To include inline images, just add an <img> tag:
<body>
<img src="https://yoursite.com/logo.png">
</body>
Use the image tag to include a media depiction:
<body>
{% image id.depiction %}
</body>
After you’ve created the template, you can send the e-mail. You can provide the template variables (we had id and sender_name in the template) as vars:
-include_lib("zotonic_core/include/zotonic.hrl").
some_function(SomeId, Sender, Context) ->
%% Create an e-mail record
Email = #email{
to = "someone@somewhere.com",
vars = [
{id, SomeId},
{sender_name, Sender}
],
html_tpl = "email.tpl"
},
%% And send the e-mail
z_email:send(Email, Context).
Send e-mail to the admin
The z_email:send_admin/3 command actually looks in three different places for determining the admin e-mail address: the config key zotonic.admin_email, then the site.admin_email key, and finally the email property of the admin user (user with id 1).
If no admin email address is found then the address wwwadmin@example.com is used, where example.com will be your site’s hostname.
Receiving E-mail
In its default configuration, Zotonic starts an SMTP server on port 2525 for receiving e-mail messages. You can write your own code to decide what happens if somebody sends e-mail to the system, by implementing the email_received notification (see below).
The SMTP server is also used to receive bounce messages from other servers, when sending of a message has failed. mod_mailinglist uses this functionality to automatically deactivate invalid e-mail addresses.
Configuring incoming E-mail
To send messages to Zotonic, the domain part of the e-mail address should have an A or MX record which points to the server where Zotonic is able to receive on port 25. This means that you have to add a firewall rule to redirect port 25 to 2525.
If you were to set up e-mail receiving for a site called example.com, you could test if this is working by using the netcat program, like this:
nc example.com 25
Then, you should be greeted by Zotonic in the following way:
220 example.com ESMTP Zotonic 1.0.0
Press ctrl-c to exit.
Handling incoming E-mail
When receiving an e-mail message, Zotonic looks at the domain part of the e-mail address to determine which Zotonic site is configured to handle this message. It looks at the host and hostalias fields in the site’s config file to match the recipient domain.
If no site matches the e-mails domain, the message is dropped, and a warning logged.
For handling incoming messages in your site, you need a hook in your site module to do something with the received messages, implementing the email_receive notification.
The code in your module looks like this:
-include_lib("kernel/include/logger.hrl").
observe_email_received(E, _C) ->
?LOG_WARNING("Email from: ~p: ~p", [E#email_received.from,
E#email_received.email#email.subject]),
ok.
Export this function and then restart your site. Now, send an e-mail message to any address @example.com, and notice that it arrives in Zotonic:
(zotonic001@host.local)9> 20:57:54.174 [warning] Email from: <<"arjan@miraclethings.nl">>: <<"Hello!">>
Feedback
If you need feedback on messages that have been sent, enable mod_logging which provides an overview of sent/received and bounced messages.
Troubleshooting
Check in the admin the log and smtp log. If a message bounces back to the Zotonic SMTP server, you will see errors there. A typical error looks like this:
SMTP: bounce: 504 5.5.2 <noreply+mlcm6godbz2cchtgdvom@oeps>: Sender address rejected: need fully-qualified address To: piet@example.com (1234) From: <noreply+mlcm6godbz2cchtgdvom@oeps>