How would i go about to receive mails in a Ruby on Rails application without going through a mail server like PostFix or to fetch them by pop3 etc.
What i was to do is to catch all mails sent to @mydomain.com and just do something with them in my application. I don't need to store the mails or anything like that.
Is this posible?
You can do this if you write your own mail server, or if your mail server supports hooks to run external programs upon receipt of mail (e.g. procmail).
If you don't have procmail available (or, if on something like Exchange Server, don't feel like writing custom rules or extensions), you're simply better off using a pop3 library to fetch mail.
Obviously, writing a mail server is more difficult than any of the alternatives.
If you're mostly worried about checking potentially hundreds of email accounts, that's solvable by configuring your email server properly. If you're on a hosted provider, ask your server administrator about creating a "catch-all" account that routes all mail to unknown addresses to a single account.
If you're aiming to avoid having to poll a server, consider the IMAP IDLE command. I've successfully written a Ruby client that opens a connection to an IMAP server, and gets told by the server when new mail arrives.
I just implemented this for my SAAS to autoprocess mailer-bounce notification messages.
Call me, call you?
You call me You can set up a local mail server. It would then respond to an incoming email, and start up a rails executable to process the email. This method is NOT recommended since starting up rails is a big task (takes multiple secs and lots of memory). You don't want a Rails bad boy started up just because you received an email. You'd be writing your own DDOS attack. (Attacking yourself.)
I call you Instead, poll for email on your own schedule by using a single job to process all currently waiting emails. You need to set up a background job handler since stock rails is focused on responding to web requests. I use delayed_job, but there are other alternatives including kicking off a cron job every so in often.
Another benefit is that you don't need to manage a mail server. Leave that headache to someone else. Then use the Ruby library net::imap to read the incoming mail and process it.
If your process doesn't recognize the email format, then forward the msg to a human for processing.
And be sure that if the process sends mail in addition to reading/processing it, that the process uses a different email address as its From address. Otherwise, odds are good that sometime along the way, you'll end up in an email loop and many gigabytes of messages going back and forth. For example, your process receives a message, responds to it, but in the meantime the sender (a human) has switched on vacation response. And your robot then responds to the vacation response..... oops....
Writing your own mail server
Re:
How would i go about to receive mails in a Ruby on Rails application without going through a mail server like PostFix or to fetch them by pop3 etc.
What i was to do is to catch all mails sent to @mydomain.com and just do something with them in my application. I don't need to store the mails or anything like that.
Direct answer: Yes, you could do this by writing an smtp server and setting up dns so your machine will be the mail destination for the domain. Your smtp server would process the messages on the fly, they would not be stored on your system at any point.
Is this a good idea? No, not at all. While appearances may be to the contrary, email is a store and forward system. Trying to avoid storing the messages before your app processes them is not smart. It would be a very very poor "optimization." However, using an access protocol (POP3 or IMAP) is a good way to avoid the costs of installing, configuring and managing a mail server.