Also morelikely you will need the help of your host provider and/or your e-mail provider. This is an optional service so you can still publish posts from the Write Post SubPanel if you don’t want to post via e-mail.

You need to Complete the following fields to post by e-mail:

Mail Server

The mail server store your email for retrieval on your behalf and thus Your mail server will have a URI address, such as mail.example.com, which you should enter here.

Port
You should enter the port number here, the Servers usually use port 110 to receive requests related to emails. If your mail server uses a different port, enter that port number here.

Login Name
If, for example, the e-mail address that you will be using for the writing by e-mail feature is yoursite@example.com, then ‘yoursite’ is the Login name.

Password

Enter the password for the above e-mail address here.

Default Mail Category

All post published via the post by email feature, WordPress will assign this Category. Note: You can also create new Categories in via Administration > Manage > Categories.

More help for the set-up, check with codex at http://codex.wordpress.org/Blog_by_Email.