Need a custom form designed

[Pauli]

For a public post folder, requirements that when user presses reply to email
message in folder;

1) It always looks like it comes from a designated user, not the user who
presses reply in public folder
2) The new email box that comes up is blank - no text whatsoever
3) User is limited to typing in max of 160 characters

Reason is reply will go to a external mailbox and be converted to SMS

Can anyone help?

Thanks