How can I prevent users from changing the "send from" address to another
user's address when they send out an email? I would like to block this
feature.

Version of Outlook?
Type of mail account?

Setting Group Policies and the correct Exchange permissions (when using
Exchange) would get you quite far already.
See http://www.howto-outlook.com/howto/policies.htm

--
Robert Sparnaaij [MVP-Outlook]
Coauthor, Configuring Microsoft Outlook 2003
http://www.howto-outlook.com/
Outlook FAQ, HowTo, Downloads, Add-Ins and more

http://www.msoutlook.info/
Real World Questions, Real World Answers

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"Linda @ Josam" <Linda @ (E-Mail Removed)> wrote in message
news:7CC5933C-2668-4B81-927F-(E-Mail Removed)...
> How can I prevent users from changing the "send from" address to another
> user's address when they send out an email? I would like to block this
> feature.