It's all pretty simple, but all the mail part uses Mailgun routes, which now require subscribing at least to the "Foundation" plan, that costs $35/month.

Fortunately my routes were already set up and still work on the Flex plan; I just can't edit them any more; but they were pretty generic so that's not too much of a problem for me; but it would be a problem for a new implementation.

Also, the code isn't pretty and since I built it for myself, it doesn't have any security feature whatsoever (no login, no sessions, no encryption, nothing).

I don't think I want to deal with all the people who would tell me how bad my code is if I published it... But for me it works.

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That said, sending emails is the easy part; it's dealing with incoming email that requires a better Mailgun plan (not just for routes but for parsing the content of the email).

If you only need a system to send you an email every day you can 1/ open a Flex account with Mailgun (no recurring fee, pay-as-you-go email) and 2/ setup a cronjob with a short script in any language that can do a POST request; here's my example in Python.

    request_url = "https://api.eu.mailgun.net/v3/yourdomain.com/messages"
    request = requests.post(request_url, auth=("api", mailgunKey), data = {
      "from": "sender <reply@yourdomain.com>",
      "to": emails,
      "recipient-variables": json.dumps(recipients),
      "subject": "%recipient.task% [%recipient.day% %recipient.date%]",
      "text": body
      })

The Mailgun API is well documented and fairly simple to use: https://documentation.mailgun.com/en/latest/api-sending.html...

(There are certainly many other providers that do the same thing.)

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PS: I'm surprised of the interest though; last time I talked about it on HN it didn't generate that many replies; someone did indeed mention a similar SaaS that folded for lack of growth. I think it's one of those things where all potential users are already here on HN...