Postmark offers "Send an Email" and "Send an Email With Templates" actions on Zapier that will, when triggered, send an email to the desired recipients. The Postmark actions in Zapier support both Transactional and Broadcast Message Streams.
An action on Zapier is a function that you can choose to happen after an event is triggered. Zapier supports over 3,000 integrations from application providers and most have triggers that you can choose to use based on events. By using a trigger and collecting the data it sent to Zapier, you can have a message composed automatically using the captured data.
Choosing the Postmark Send an Email Action
The first thing you'll need to do when connecting your Zapier account to Postmark, is to choose a trigger event that will cause Postmark to send an email. Let's select the Google Sheets trigger to then the Postmark "Send an Email" action when a row is added or updated to a Spreadsheet.
Connecting Your Google Account
Now that you've selected the trigger and action you'd like to take, you'll need to connect your Google account. Have your Google account and Google Sheet information handy, and enter the data into the respective fields when Zapier asks for it. This will verify and link up your Google account.
Connecting Your Postmark Account
Next you'll be prompted to connect your Postmark account. In the API Tokens tab in the settings of the Postmark Server you want to use for this integration, copy the "Server API Token" from the text box and paste it to the X-Postmark-Server-Token field in the Zapier display when asked. Zapier will then confirm your Postmark account.
You'll then choose your Action Event, either "Send an Email" or "Send Email With Template". In this example, we'll use "Send an Email".
Creating Your Email Template
Map the fields from the Google Sheets data into the email you'd like to compose to your recipients. The Zapier interface is quite flexible and allows you to mix ad-hoc text with field data from Google Sheets (or any trigger you choose to integrate with). You'll have the option to add a Message Stream value, by default this is set to the "outbound" Stream in your server. This flexibility allows you to send through Broadcast and Transactional Streams through Zapier.
Finally, confirm your Zap and turn it on. Now, each time a new row is created or updated in Google Sheets, your recipients will be notified by email through your Postmark Server.