Stealth Mode

What is stealth mode and why would you want to turn this feature on? Will having this feature on affect incoming emails?

No, what stealth mode does is when someone pings you, your computer doesn't return an answer to the ping. So as far as they know, your computer doesn't exsist.

Wont affect mail. Only works on ports you have turned off.

cradom is right Stealth mode makes no acknowledgement to any uninvited contact from other computers...

From Apple:

Stealth mode

When you enable stealth mode, all uninvited data traffic receives no response from your computer. Stealth mode virtually hides your computer behind your firewall, and other computers sending traffic to your computer receive no information about your computer.

Click to expand...

http://docs.info.apple.com/article.html?path=Mac/10.4/en/mh1242.html

You will notice however when doing a free online security port scan that even though stealth is on it is still reported as open with stealth on. Also when behind a router stealth means nothing to the internet.

Having it on will not harm email. Or an services you are running ie file sharing, printer sharing or web sharing.