Invismail works in 5.1!!!

I only found this out by accident, someone mentioned that it worked, as none of the APIs it uses has changed. They, I've forgotten who now, said all it needs was a .info file.

so I save something like this as invisimail.info

; $Id: invisimail.info,v 1.3 2006/11/21 20:55:33 dries Exp $
name = Invisimail
description = Encrypt email.
package = Core - optional
version = VERSION

; Information added by drupal.org packaging script on 2007-01-30
version = "5.1"
project = "drupal"

so I downloaded invisimail and save the code above into the invisimail module directory.

After that you still gotta go to site config>input formats and configure your input formats to encode email addresses.
which isn't mentioned in the README file
you also need the Email module, but that's also okay for 5.x

someone could add an info file to the download to upgrade it, and save other people hours of hunting for stuff

Patch is already pending: http://drupal.org/node/112785