Got this from a thread @Brighthand started by user Ed Hardy:

POP3

If you want to be able read and respond to your emails when you're offline, you can download then with the basic POP3 service. This is convenient, but the setup process is not. Here are the settings I used:

Account Name: (Something like Personal or Gmail)
Account Type: POP3

Hit Next

Name: (The name you want to be on your outgoing emails)
User name: XXXXXXX@gmail.com
Password: *******
E-mail Address: XXXXXXX@gmail.com (same as User Name)

Hit Next

Incoming server: pop.gmail.com
Outgoing server: smtp.gmail.com
Use connection-specific SMTP servers: No (Don't hit the check mark)

Hit Next

The next page tells you setup is complete, but it's not. Hit the button labeled "Advanced".

On the Incoming Tab
Retrieve: (Your choice)
Leave Messages on server: (You probably want to select this, or you won't
be able to read your messages online any more)
Password authentication: Normal
Security: SSL (POP3S)
Incoming e-mail port: 995

On the Outgoing Tab:
SMTP authentication: Login
User name: XXXXXXX@gmail.com
Password: *******
Security: SSL
Outgoing e-mail port: 465

Hit OK

Hit Finish


IMAP

I briefly set up Gmail's IMAP service, but quickly switched back to POP3. It was painfully, agonizingly slow. Opening each message required the N810 to go to Google servers and this took minutes every time.

Unless someone else with a better experience can chime in, I'd suggest you avoid using this service.


Setting for POP3 and IMAP

Open the Drop-down box, pick Tools, then Settings.

Update automatically: (I have this turned off, because there's no way
to set the times when you'll get messages. I got tired
of being woken up at midnight with a new email.)
Update when connected via: (this is handy)
Update Interval: (Your choice, but keep in mind frequent updates
will affect your battery life.)