Send an unlimited amount of emails from your own gmail or google domain. There is no pay-as-you-go scheme just a fixed $5.00 usd per month.
An email can be completely formatted with bbcode or html.
Use the same action to send from any of your alias accounts.
You can fully customize your emails with the provided Expert Mode and design your emails in real-time at Thirdsoft Email Template Generator
There are also free resources you can find to design emails Here, just copy the html code from a free template.