Well, of course, but I'll put in some more though if it gets anywhere near that (like ads or some sort). Running lambdas are really cheap. Realistically, the image conversion costs will not surpass monthly free tier unless I'm trigger 1.6 million emails a month. The expensive bit by far would come to the file storage which is something I'll figure out later

The idea is fun, but in reality the contents is not that interesting.

What would make someone come back to the site, since you mentioned ads.

oh dont get me wrong, there is almost 0 value to this site outside of a little chuckle from myself that it worked. I'll only add ads in that very slim case where it starts costing me money

Which is probably why Mailinator has paid versions for teams and enterprise.

https://www.mailinator.com/v3/#/#pricing_table_pane