The new mailing list system "mailman" is very strict with subscriptions to prevent spammers to flood the mailing lists. If you post to a GRASS list and receive a message similar to:
Subject: Your message to grass5 awaits moderator approval The reason it is being held: Post by non-member to a members-only list
you are using two different senders. Such message won't come through to the list. Be sure that the "From:" setting is matching your subscription.
What about the "reply to" settings:
If you are annoyed that the "reply" to function of your mailtool send mails back to the original sender instead of the GRASS list, you will have to study the manual of your preferred mailing list software how to manage lists. You will search for a "list reply" function.
Here are some hints for mail software: