Added Postmark ingress support

1 files changed, 36 insertions, 0 deletions

diff --git a/guides/source/action_mailbox_basics.md b/guides/source/action_mailbox_basics.md
index eb8a14b4d2..f2c8a0a6b7 100644
--- a/guides/source/action_mailbox_basics.md
+++ b/guides/source/action_mailbox_basics.md
@@ -155,6 +155,42 @@ would look like this:
 $ URL=https://example.com/rails/action_mailbox/postfix/inbound_emails INGRESS_PASSWORD=... rails action_mailbox:ingress:postfix
 ```
 
+### Postmark
+
+Tell Action Mailbox to accept emails from Postmark:
+
+```ruby
+# config/environments/production.rb
+config.action_mailbox.ingress = :postmark
+```
+
+Generate a strong password that Action Mailbox can use to authenticate
+requests to the Postmark ingress.
+
+Use `rails credentials:edit` to add the password to your application's
+encrypted credentials under `action_mailbox.ingress_password`,
+where Action Mailbox will automatically find it:
+
+```yaml
+action_mailbox:
+  ingress_password: ...
+```
+
+Alternatively, provide the password in the `RAILS_INBOUND_EMAIL_PASSWORD`
+environment variable.
+
+[Configure Postmark inbound webhook](https://postmarkapp.com/manual#configure-your-inbound-webhook-url)
+to forward inbound emails to `/rails/action_mailbox/postmark/inbound_emails` with the username `actionmailbox`
+and the password you previously generated. If your application lived at `https://example.com`, you would
+configure Postmark with the following fully-qualified URL:
+
+```
+https://actionmailbox:PASSWORD@example.com/rails/action_mailbox/postmark/inbound_emails
+```
+
+NOTE: When configuring your Postmark inbound webhook, be sure to check the box labeled **"Include raw email content in JSON payload"**.
+Action Mailbox needs the raw email content to work.
+
 ### SendGrid
 
 Tell Action Mailbox to accept emails from SendGrid: