Both anonymous and active members become Undeliverable when the application encounters three failures in a row in attempting to deliver mail. Each email invitation or communication is considered an individual instance of failure, if the email cannot be delivered to a particular recipient.
The following are possible causes of email delivery failure:
- There is a either a block or deferral (temp block) against the community based on the community's sender reputation.
- The recipient’s email address is invalid (for example, there is a typo in the email address).
- The recipient’s domain is invalid (for example, @yahoo.com).
- The application was unable to deliver an email after 24 hours due to issues with the ISP.