# Postmark Enables ngSurvey to use PostMark's email sending API. ## 🔅 Postmark properties * **`Server API token`**is the token provided by your Postmark account for sending emails. * **`Webhook handler`**can be used and set within your Postmark account to track bounced and invalid emails. * **`Restrict globally to one sender`** if enabled it allow us to specify one email and name that will be used for all email sending processes within ngSurvey. If activated ngSurvey will only use the email specified and will not use anymore the user account email and wont allow the user to enter any email for any of the email features like campaigns, tasks. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.ngsurvey.com/installation-setup/system-settings/mailing-server/iis-smtp-exchange-server-1.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.