Email on Acid offers both monthly and pay-as-you-go pricing. Monthly pricing starts at $55/month (or $44/month when paid annually). Pay-as-you-go pricing is available for $10 per test (minimum $50 purchase).
Email on Acid offers screenshot previews of your email designs from over 30 email clients.
Other features include SPAM filter testing, analytics, web page testing, Mozify (for image blocking), and more.
Litmus pricing starts at $99/month (or $79/month when paid annually).
Litmus offers screenshot previews of your email designs from over 50 email clients.
In addition to screenshot previews, Litmus offers live “interactive” testing. Live testing allows you to access any email client on a virtual machine and interact with how your design behaves. You can even edit your email design and see it updated in real-time.
Other features include SPAM filter testing, analytics, web page testing, and more.