I just migrated my website to Ghost this past weekend and tried setting up Mailgun using my existing account. Every time I attempt to send emails, I keep getting this error message:
421 Domain is not allowed to send: Free accounts are for test purposes only. Please upgrade or add the address to your authorized recipients.
I contacted their support team but got transferred around several times. They finally told me I need to upgrade to their paid plan, but they closed my support ticket before I could ask about cheaper alternatives to their $15 monthly subscription:
This error occurs whenever sending through a sandbox domain without inviting users called Authorized Recipients. The free plan, which is intended for test usage, only allows use of the sandbox domain and the associated Authorized Recipients. With the upgraded plans, which are intended for production usage, custom domains can be added to the account and used without the need for Authorized Recipients
I’m pretty sure Mailgun used to offer a pay-per-use option, but I can’t find any way to add payment details without committing to their monthly plan. Since my blog is still small, I can’t really justify spending $15 every month on email services.
UPDATE (2025-06-18):
Apparently you have to completely delete your Mailgun account first, then you’ll see the “Flex (Pay as you Go)” option when creating a new one. I discovered this tip on a Ghost community forum.
But when I try to switch, I get an error message saying to contact support, so the problem isn’t fixed yet
Had this exact issue three months ago. The waiting period after deletion varies - mine took 72 hours before the system completely cleared my email from their database. I tried using a different email address for the new account during that time and it worked immediately. Once you get the flex plan activated, verify your domain properly because the sandbox restrictions carry over if verification fails. The domain verification takes about 15-20 minutes but saves you from hitting the authorized recipients limitation again. Flex pricing changed recently - it’s now $0.80 per thousand for the first 5k emails, then drops to $0.60 per thousand after that. Still much better than the $15 monthly fee for small operations.
mailgun’s signup is needlessly complicated. i hit the same wall - switched to a completely different email provider (gmail to yahoo) instead of waiting for account deletion. worked instantly and got flex pricing immediately. double-check your dns after domain verification too. mine kept reverting to sandbox because one txt record wasn’t propagating right.
Same thing happened to me last month when I switched to Ghost. The delete/recreate trick works, but you’ve got to wait 24-48 hours after deleting before making a new account. Try recreating immediately and their system still recognizes your email - blocks the flex option completely. I rushed it and got stuck dealing with support for three days. Waited the full two days, made a fresh account with the same email, and boom - pay-as-you-go showed up during signup. Flex plan starts at $0.80 per thousand emails, which beats their monthly subscription if you’re running a small blog.