Amazon Simple Email Service
$0.10 per 1,000 emails sent. 65K free emails per month if you are hosted on EC2.
Disadvantage: You can only sent from @your-domain.extn, if you have a SAS application and need to sent from some other email address, you need domain added to SES and verified.
Free account allow you to send 6,000/- email per month with 200 mails per day limit. Paid plan start at $9.65 per month for 30k emails.
Pay as you go plan start at $0.80 / 1000 emails.
Pay as you go plan start at $0.09/1000 emails
50K Emails for $9 per month. If you are on AWS, you can get it cheaper from marketplace.
40K email per month for $9.95 per month.