Ram: > I dont think <> is supported in a hash: file It is a special pattern for SMTPD access maps (i.e. this is implemented in the Postfix access map code, not in the code that implements hash or other databases).
smtpd_null_access_lookup_key (default: <>) The lookup key to be used in SMTP access(5) tables instead of the null sender address. Wietse