Why are you posting about this in a Word newsgroup?
Ctrl+Z is Undo. It sounds like you're accidentally pressing Ctrl+Z.
Unfortunately, Outlook does not let you reassign keys. Word does, however.
If you're using Word as your email editor (version?), try tools -
customize - keyboard; find the EditUndo command, and remove the Ctrl+Z
assignment. I don't have a version of Office that lets you use Word as the
editor for Outlook, so I can't test to see if such reassignment is
recognized or retained when using Word in that way.
Alternatively... Ctrl+Y undoes a Ctrl+Z. That's certainly faster than going
through the Edit menu option.
--
Herb Tyson MS MVP
Author of the Word 2007 Bible
Blog:
http://word2007bible.herbtyson.com
Web:
http://www.herbtyson.com