Archivers, what they archive, how to download. Numbering has been added to the questions list to aid in finding things. 2.19 Elm seems to ignore HOME environment variable. Elm uses the MAIL environment variable to read the correct mailbox. This can be any text file, but usually signatures are 4 lines or less.
Any reply is qualified to prevent alias expansion.
If you had an alias in your private Elm aliases that matched the name of a user on your system, but that alias did not point to that user, there would be no way to reply to the message. It would end up going to the alias name, not the user that mailed you. This makes the simplistic signature detector think that the message is 'remote'. This is not slated to change until 3.0. You can't and don't want to.