“Hardware”

Remaildr is hosted on an Amazon EC2 micro instance, benefiting of the free tier offer. Apart from the static IP that will probably end up costing me something, remaildr should be about free.

— Edit: as of may, remaildr is now hosted on a VPS at OVH. The EBS volume of my EC2 instance blew up on me, and with the free tier coming to end, EC2 would be too costly.

Network

The remaildr.com domain is registered at OVH, because of the low price and the flexibility they allow on DNS. I added an A record for mail.remaildr.com pointing to 50.16.218.96 —the AWS elastic IP—, then modified the MX record for remaildr.com to point to mail.remaildr.com. That way, every email sent to any_address@remaildr.com will be sent to the right mail server. Having an A record also allows reverse DNS on the mail server, often used to flag spam.

Other DNS modifications included the SPF record, which allows the mail server to actually send emails in behalf of remaildr.com, and a TXT record for DKIM — cryptographically signing outgoing emails.

OVH provides a free 1MB web storage for each domain name subscription, which is more than enough to host the remaildr.com website, weighing about 30KB.

The mail server

The email server at OVH is a run-of-the-mill Debian Squeeze. It runs a Postfix server, configured to forward a few specific email addresses (for example abuse, postmaster and info) to my account, and let everything else go to a catch-all account called remind.

A set of two Daemonized Ruby scripts will then do all the work:

• receivr.rb will fetch the emails in POP, compute the send date, then put the remaildr to send back into a PostgreSQL database as a Base64-encoded marshalled ruby object (akin to how DelayedJobs works as far as I understand)
• sendr.rb will read the database and send all the emails who need to be sent

Of course, the code is on GitHub.

That’s about it! Feel free to ask any questions, and I’ll answer as well as I can. :)