Postcard is now open source

This looks great but delivery via Amazon SES is a problem. I'm an academic and I tried to set up a work newsletter like this with Listmonk recently, but SES rejected my request to relieve me of sandbox mode for unspecified 'security reasons'. Everything was set up properly, it was under a domain under my personal name, I gave links to my profile page on my university website, ample explanation about what I would do with it (one email ever few months), that I would be the only sender, but they rejected it. So in the end I've opted for a hosted solution... anyone else had similar issues?

Postcard originally used Postmark. But, Postmark deliverability has been decreasing. And, for the open-source version, I wanted to simplify dependencies. So, I moved it to SES. It works for small lists, but won't scale to massive ones.

I welcome PRs to add additional sending providers - it wouldn't be onerous.