Sometimes wordpress email capabilities is just not enough for your needs, this is the exact scenario where you need a good plugin to resolve your problem. here are some excellent Email plugins for wordpress:
WP Better Emails
Adds a customizable good looking HTML template to all WP default plain/text emails and lets you set a custom sender name and email address.
Simple plugin for mailing news or updates to members registered on the blog.
Sends a list of subscribers an email notification when new posts are published to your blog
Style your html and plain text mails with dedicated themes and templates.
Double opt-in subscription.
Subscriptions to Comments, Newsletters/Post notifications and even to Mailing lists.
Newsletters/Post notifications on a per post, daily, weekly, monthly basis.
Optional : full control on all mails sent by WordPress.
Converts the default plain text email notifications into fully customizable, sweet-lookin’ HTML emails.
Newsletter is a plug-in to collect subscribers and send out newsletters.