Boses wife and smart phone

Hi all

I have an exchange 2003 server sp1 running very well. All remote users access the server via RPC over HTTPS and this is working great. Now the boses wife has a Motorolla smart phone, (around 6 months old) she wantes to get her email on the phone. The only way i can get this to work is if i open up port 143 on my firewall for imap. I do not see anything in this phone for active synch or windows mobile. Is opening up this port to my exchange server a security issue? alos if she deletes an email from the phone is it also deleted from the server?

Thanks