Accessing Postmark Message ID

Each email message sent by Postmark will contain a unique Postmark message ID. In case of email messages, identifier is stored within X-PM-Message-ID header.

This identifier can be used to for things like retrieving bounce detailslater.

The example below shows you how to access the Postmark Message ID from sent email headers.

server_token = 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'
client = Postmark::ApiClient.new(server_token)

message = Mail.new
# ...
client.deliver_message(message)
message['X-PM-Message-ID'].to_s

# => cadba131-f6d6-4cfc-9892-16ee738ba54c

You can also access Postmark message ID from sent email response. In this case, identifier is accessible by :message_id.

client.deliver({from: '[email protected]', to: '[email protected]', html_body: 'test', subject: 'Welcome email'})

{:to=>"[email protected]",
 :submitted_at=>"2021-07-05T12:55:25.6949168Z",
 :message_id=>"123456-111c-111-1234567890",
 :error_code=>0,
 :message=>"OK"}

Postmark message id is stored within "X-PM-Message-ID" header, not "Message-ID" header of the email sent for reason of not altering any identifiers which are not Postmark related. Postmark related headers will always start with "X-PM" to not interfere any other headers.