Fixed env var for backup config - related to #14964

[snipe]

We were using the incorrect mail variable in the backup config, MAIL_FROM_ADDRESS , vs MAIL_FROM_ADDR. Thanks for finding that, @triple-HA!

[what-the-diff]

PR Summary

• Email Address Configuration Change
  The configuration of the system's email sender address has been updated. Specifically, in the configuration settings, the tag that holds the value of the email sender's address has been changed from MAIL_FROM_ADDRESS to MAIL_FROM_ADDR. This just means we've updated the label of how we store the system's "From" email address; the actual email address being used by the system has not been changed.