Verified email not sending through Heroku/Mailgun

So the issue turned out to be that when I verified my custom domain it created a second domain under my Heroku/Mailgun account. I still had the credentials from the xxx.mailgun.org (sandbox) domain in my Heroku env vars. Once I replaced them with the credentials from my custom domain everything worked. (Since Heroku set the first set of env vars I foolishly assumed the new set would get put in automatically.) Sigh...

Thanks for your help lyen.

To add on to lostphilosopher answer, I recently solved this MailGun custom domain issue myself.

Here's what worked for me:

Situation: After successfully adding a custom domain to Mailgun, my mail sending/receiving stopped working

Errors: After adding custom domain and verifying DNS with Mailgun, I received error messages such as:

Net::SMTPFatalError: 554 Sandbox subdomains are for test purposes only. Please add your own domain or add the address to authorized recipients in Account Settings.

Solution: Realize that Heroku does NOT automatically update configuration variables for you. You must manually update them with values for your new domain.

1. In MailGun - Find your new MailGun domain settings under under https://mailgun.com/app/domains
2. In Heroku - goto: Heroku > App > Settings > Reveal Config Vars
3. In Heroku - Update the following config vars
   • MAILGUN_DOMAIN
   • MAILGUN_SMTP_LOGIN
   • MAILGUN_SMTP_PASSWORD

And yes I agree - MailGun docs are not the most thorough. Especially when it comes to testing your setup.

Did you add the recipients of your e-mail to "Authorized Recipients" list under https://mailgun.com/app/domains/sandbox_your_domain.mailgun.org?

Be sure to add a real e-mail address which can receive e-mails.

This is because mailgun would send a confirmation e-mail asking if the owner of the e-mail address really wants to receive e-mails from mailgun.