When a fax you send fails to deliver, the fax will retry automatically before it is reported as a failure.

The flow is:

  1. Fax sending is attempted, but fails
  2. Fax transmission waits
  3. Fax sending is attempted again, but fails
  4. Fax is marked as a failure and the sender is notified

By default, faxes are retried 10 minutes after the first failure. There are two places this could be changed:

  1. Your sending email address's configuration can be updated so faxes are reattempted on a different schedule (eg retried 3 times with 5 minutes in between)
  2. Limited by the failure type (eg "Voice" failures are limited, whereas "Busy" failures are not limited

Failure types that limit the duration and frequency of retries:

  • Bad Number
  • Invalid Number Format
  • Unallocated Number
  • No Answer
  • Voice