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Product tier: Available to all subscription tiers

Greenhouse uses Mailgun, a third-party service, to send customer emails. However, Greenhouse provides a Custom SMTP setup option for customers who prefer to send emails via their own organization's architecture. In this article, we'll provide a brief overview of the Custom SMTP setup options.


When using Custom SMTP, Greenhouse Recruiting first will send all emails to one of our SMTP servers, which are then relayed to your organization's mail server. The relay allows us to guarantee that all of our SMTP messages originate from one of a set of known IP addresses. You will need to allowlist each of the IP addresses and accept all messages sent by these machines.


Note: When using a Custom SMTP configuration to send emails, your internal IT team will be required to troubleshoot any email-related issues. Our support team will not be able to help diagnose errors or issues that occur after the email has been triggered from Greenhouse.

For a Custom SMTP configuration, Greenhouse requires you to provide:

  • Host name of the server
  • Port Number
  • Optional: Username of the server (not the credentials of an individual user's mailbox)
  • Optional: Password of the server (not the credentials of an individual user's mailbox)

Additionally, your organization will need to allowlist a set of IP addresses that we provide. For more information about the list of IP addresses that will need to be allowlisted for full functionality, please click here.

For more information regarding Custom SMTP, contact Customer Support.