Mailchimp is an obvious alternative - but will only run a scheduled RSS notification. In the past I have found that quite useful though - because I get to correct errors before the notification goes out.
Mailchimp (bulk email sender) is not really an alternative to Mailgun (transactional email provider that also supports INCOMING mail routing)… let alone an “obvious” one. Unless you’re referring to Mandrill, Mailchimp’s transactional email service, which is a PAID add-on that can only be added to a PAID Mailchimp account.
I manage a couple of Postmark accounts on behalf of clients. It’s a solid service, just like Mailgun and all the rest.
Their free tier allows just 100 emails per month though, which is barely enough for testing purposes. And if I have to pay then I’d rather stay with the Mailgun that I’ve used for years.
For my own use, I’m currently using AWS SES for both transactional and bulk emails, using FreeCodeCamp’s Mail for Good as a front-end to manage my newsletters and bulk email campaigns. Yet to do any integration with Ghost.
To be clear: Mailgun is still free for 625 emails per month - they don’t bill for any charges less than $0.50.
Whether you’re sending more or less than 625 emails a month, Mailgun still works out cheaper and more convenient than pretty much any other option mentioned here.
If you want to optimise for quality, most of the other products mentioned in this topic are far superior. But for people reading this trying to optimise for cost: The cheapest/free option which makes most sense for most people is still Mailgun.
Direct quote from Mailgun customer notification:
On March 1, 2020, we will automatically transition your account to the new Flex plan, a pay-as-you-go plan comparable to the Concept plan you’re currently on. You’ll receive your first invoice under the new plan on April 1 if your amount due is greater than $0.50.