How can I send emails using my own mail server in Meteor?

I am trying to enable email support for my Meteor application, and since I have my own server I want to also use my own mail server. So I installed postfix in my Debian wheezy server and successfully sent and email to my GMail address, so that means the mail server works properly and sends emails.

When I deploy my Meteor app and try to send an email though, say to do a password reset, my app crashes with the following error:

Exception while invoking method 'forgotPassword' RecipientError: Can't send mail - all recipients were rejected
at Object.Future.wait (/home/loupax/phial/bundle/programs/server/node_modules/fibers/future.js:326:15)
at smtpSend (packages/email/email.js:94)
at Object.Email.send (packages/email/email.js:155)
...
...

My MAIL_URL environment variable is in the format MAIL_URL=smtp://my_domain.tld.