# Snip from /etc/postfix/main.cf

smtpd_recipient_restrictions =
  permit_mynetworks
  reject_non_fqdn_hostname
  reject_invalid_hostname
  reject_unknown_sender_domain
  check_sender_access hash:/etc/postfix/sender_access
  check_policy_service unix:private/tumgreyspf

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What should the /etc/postfix/sender_access file look like?