Personal and corporate email security controls are important as sensitive information may be occasionally exchanged via email.  The ISC site notes the importance of these controls. 

Secure E-Mail Access
http://isc.sans.edu/diary.html?storyid=12544

QUOTE: Recently attacks focused on e-mail security. In many cases, e-mail credentials were either brute forced, or retrieved from compromised databases (in some of these cases, password re-use was a contributing factor). Some of the challenges:

– the use of “cloud based” e-mail services like gmail.
– mobile access to e-mail
– access to e-mail from multiple devices
– e-mail encryption and authentication (PGP/S-Mime)
– e-mail forwarding security (if someone has e-mail forwarded to a personal e-mail address)