phorge / src / docs / user / configuration / configuring_inbound_email.diviner

@title Configuring Inbound Email
@group config

This document contains instructions for configuring inbound email, so users
may interact with some Phorge applications via email.

Preamble
========

Phorge can process inbound mail in two general ways:

**Handling Replies**: When users reply to email notifications about changes,
Phorge can turn email into comments on the relevant discussion thread.

**Creating Objects**: You can configure an address like `[e-mail]`
to create new objects (like tasks) when users send email.

In either case, users can interact with objects via mail commands to apply a
broader set of changes to objects beyond commenting. (For example, you can use
`!close` to close a task or `!priority` to change task priority.)

To configure inbound mail, you will generally:

  - Configure some mail domain to submit mail to Phorge for processing.
  - For handling replies, set `metamta.reply-handler-domain` in your
    configuration.
  - For handling email that creates objects, configure inbound addresses in the
    relevant application.

See below for details on each of these steps.


Configuration Overview
======================

Usually, the most challenging part of configuring inbound mail is getting mail
delivered to Phorge for processing. This step can be made much easier if
you use a third-party mail service which can submit mail to Phorge via
webhooks.

Some available approaches for delivering mail to Phorge are:

| Receive Mail With | Setup | Cost | Notes |
|--------|-------|------|-------|
| Postmark | Easy | Cheap | Recommended |
| SendGrid | Easy | Cheap | |
| Mailgun | Easy | Cheap | Discouraged |
| Local MTA | Difficult | Free | Discouraged |

The remainder of this document walks through configuring Phorge to
receive mail, and then configuring your chosen transport to deliver mail
to Phorge.


Configuring "Reply" Email
=========================

By default, Phorge uses a `[e-mail]` email address
as the "From" address when it sends mail. The exact address it uses can be
configured with `metamta.default-address`.

When a user takes an action that generates mail, Phorge sets the
"Reply-To" address for the mail to that user's name and address. This means
that users can reply to email to discuss changes, but: the conversation won't
be recorded in Phorge; and users will not be able to use email commands
to take actions or make edits.

To change this behavior so that users can interact with objects in Phorge
over email, change the configuration key `metamta.reply-handler-domain` to some
domain you configure according to the instructions below, e.g.
`phorge.example.com`. Once you set this key, email will use a
"Reply-To" like `[e-mail]`, which -- when
configured correctly, according to the instructions below -- will parse incoming
email and allow users to interact with Differential revisions, Maniphest tasks,
etc. over email.

If you don't want Phorge to take up an entire domain (or subdomain) you
can configure a general prefix so you can use a single mailbox to receive mail
on. To make use of this set `metamta.single-reply-handler-prefix` to the
prefix of your choice, and Phorge will prepend this to the "Reply-To"
mail address. This works because everything up to the first (optional) '+'
character in an email address is considered the receiver, and everything
after is essentially ignored.


Configuring "Create" Email
==========================

You can set up application email addresses to allow users to create objects via
email. For example, you could configure `[e-mail]` to
create a Maniphest task out of any email which is sent to it.

You can find application email settings for each application at:

{nav icon=home, name=Home >
Applications >
type=instructions, name="Select an Application" >
icon=cog, name=Configure}

Not all applications support creating objects via email.

In some applications, including Maniphest, you can also configure Herald rules
with the `[ Content source ]` and/or `[ Receiving email address ]` fields to
route or handle objects based on which address mail was sent to.

You'll also need to configure the actual mail domain to submit mail to
Phorge by following the instructions below. Phorge will let you add
any address as an application address, but can only process mail which is
actually delivered to it.


Security
========

The email reply channel is "somewhat" authenticated. Each reply-to address is
unique to the recipient and includes a hash of user information and a unique
object ID, so it can only be used to update that object and only be used to act
on behalf of the recipient.

However, if an address is leaked (which is fairly easy -- for instance,
forwarding an email will leak a live reply address, or a user might take a
screenshot), //anyone// who can send mail to your reply-to domain may interact
with the object the email relates to as the user who leaked the mail. Because
the authentication around email has this weakness, some actions (like accepting
revisions) are not permitted over email.

This implementation is an attempt to balance utility and security, but makes
some sacrifices on both sides to achieve it because of the difficulty of
authenticating senders in the general case (e.g., where you are an open source
project and need to interact with users whose email accounts you have no control
over).

You can also set `metamta.public-replies`, which will change how Phorge
delivers email. Instead of sending each recipient a unique mail with a personal
reply-to address, it will send a single email to everyone with a public reply-to
address. This decreases security because anyone who can spoof a "From" address
can act as another user, but increases convenience if you use mailing lists and,
practically, is a reasonable setting for many installs. The reply-to address
will still contain a hash unique to the object it represents, so users who have
not received an email about an object can not blindly interact with it.

If you enable application email addresses, those addresses also use the weaker
"From" authentication mechanism.

NOTE: Phorge does not currently attempt to verify "From" addresses because
this is technically complex, seems unreasonably difficult in the general case,
and no installs have had a need for it yet. If you have a specific case where a
reasonable mechanism exists to provide sender verification (e.g., DKIM
signatures are sufficient to authenticate the sender under your configuration,
or you are willing to require all users to sign their email), file a feature
request.


Testing and Debugging Inbound Email
===================================

You can use the `bin/mail` utility to test and review inbound mail. This can
help you determine if mail is being delivered to Phorge or not:

  phorge/ $ ./bin/mail list-inbound   # List inbound messages.
  phorge/ $ ./bin/mail show-inbound   # Show details about a message.

You can also test receiving mail, but note that this just simulates receiving
the mail and doesn't send any information over the network. It is
primarily aimed at developing email handlers: it will still work properly
if your inbound email configuration is incorrect or even disabled.

  phorge/ $ ./bin/mail receive-test   # Receive test message.

Run `bin/mail help <command>` for detailed help on using these commands.


Mailgun Setup
=============

To use Mailgun, you need a Mailgun account. You can sign up at
<https://www.mailgun.com>. Provided you have such an account, configure it
like this:

  - Configure a mail domain according to Mailgun's instructions.
  - Add a Mailgun route with a `catch_all()` rule which takes the action
    `forward("https://phorge.example.com/mail/mailgun/")`. Replace the
    example domain with your actual domain.
  - Configure a mailer in `cluster.mailers` with your Mailgun API key.

Use of Mailgun is discouraged because of concerns that they may not be a
trustworthy custodian of sensitive data.
See <https://secure.phabricator.com/T13669> for discussion and context.

Postmark Setup
==============

To process inbound mail from Postmark, configure this URI as your inbound
webhook URI in the Postmark control panel:

```
https://<phorge.yourdomain.com>/mail/postmark/
```

See also the Postmark section in @{article:Configuring Outbound Email} for
discussion of the remote address allowlist used to verify that requests this
endpoint receives are authentic requests originating from Postmark.


SendGrid Setup
==============

To use SendGrid, you need a SendGrid account with access to the "Parse API" for
inbound email. Provided you have such an account, configure it like this:

  - Configure an MX record according to SendGrid's instructions, i.e. add
    `phorge.example.com MX 10 mx.sendgrid.net.` or similar.
  - Go to the "Parse Incoming Emails" page on SendGrid
    (<http://sendgrid.com/developer/reply>) and add the domain as the
    "Hostname".
  - Add the URL `https://phorge.example.com/mail/sendgrid/` as the "Url",
    using your domain (and HTTP instead of HTTPS if you are not configured with
    SSL).
  - If you get an error that the hostname "can't be located or verified", it
    means your MX record is either incorrectly configured or hasn't propagated
    yet.
  - Set `metamta.reply-handler-domain` to `phorge.example.com`
    (whatever you configured the MX record for).

That's it! If everything is working properly you should be able to send email
to `[e-mail]` and it should appear in
`bin/mail list-inbound` within a few seconds.


Local MTA: Installing Mailparse
===============================

If you're going to run your own MTA, you need to install the PECL mailparse
extension. In theory, you can do that with:

  $ sudo pecl install mailparse

You may run into an error like "needs mbstring". If so, try:

  $ sudo yum install php-mbstring # or equivalent
  $ sudo pecl install -n mailparse

If you get a linker error like this:

  COUNTEREXAMPLE
  PHP Warning:  PHP Startup: Unable to load dynamic library
  '/usr/lib64/php/modules/mailparse.so' - /usr/lib64/php/modules/mailparse.so:
  undefined symbol: mbfl_name2no_encoding in Unknown on line 0

...you need to edit your php.ini file so that mbstring.so is loaded **before**
mailparse.so. This is not the default if you have individual files in
`php.d/`.

Local MTA: Configuring Sendmail
===============================

Before you can configure Sendmail, you need to install Mailparse. See the
section "Installing Mailparse" above.

Sendmail is very difficult to configure. First, you need to configure it for
your domain so that mail can be delivered correctly. In broad strokes, this
probably means something like this:

  - add an MX record;
  - make sendmail listen on external interfaces;
  - open up port 25 if necessary (e.g., in your EC2 security policy);
  - add your host to /etc/mail/local-host-names; and
  - restart sendmail.

Now, you can actually configure sendmail to deliver to Phorge. In
`/etc/aliases`, add an entry like this:

  phorge: "| /path/to/phorge/scripts/mail/mail_handler.php"

If you use the `PHABRICATOR_ENV` environmental variable to select a
configuration, you can pass the value to the script as an argument:

  .../path/to/mail_handler.php <ENV>

This is an advanced feature which is rarely used. Most installs should run
without an argument.

After making this change, run `sudo newaliases`. Now you likely need to symlink
this script into `/etc/smrsh/`:

  sudo ln -s /path/to/phorge/scripts/mail/mail_handler.php /etc/smrsh/

Finally, edit `/etc/mail/virtusertable` and add an entry like this:

  @yourdomain.com phorge@localhost

That will forward all mail to @yourdomain.com to the Phorge processing
script. Run `sudo /etc/mail/make` or similar and then restart sendmail with
`sudo /etc/init.d/sendmail restart`.