  * provide feature "builder" when needed crate is in Debian
    * mail-builder
  * provide feature "dkim" when needed crate is in Debian
    * mail-auth
  * provide feature "parser" when needed crate is in Debian
    * mail-parser
  * provide features "aws_lc_rs" and "fips"
    when needed crate is in Debian
    * aws-lc-rs
