Mailgun 'Poor Mailing List': Why Your Domain Was Disabled and What the Support Ticket Needs

Remove every bouncing address, verify the rest of the list, then open a support ticket that explains where the addresses came from and whether they're double opt-in. That's what Mailgun asks for before it re-enables a domain disabled with the "Poor mailing list" error. There's no button to press; support turns sending back on.

Sources, read 2 November 2026: Mailgun's help articles Why did I receive the error "Poor mailing list"?, Why has my domain been disabled?, Suppressions and hourly sending limitation.

What happened

Mailgun says "Poor mailing list" means too many of the messages you submitted bounced because the addresses were invalid, and that when the share of bounced messages gets too high it disables the domain automatically, to protect your domain's reputation and its own IPs. It doesn't publish the threshold (we compared the platforms that do in bounce rate thresholds by platform). It does say the number one reason it sees senders blocked is a bad mailing list, and that such lists tend to contain bad addresses and spam traps.

What the support ticket needs

From Mailgun's own list:

Mailgun asks	What to write
List cleaned, bouncing addresses removed	Say how: suppression export removed, rest of list verified, count before and after
How you obtain the addresses	Signup form, checkout, app registration; link the form or portal
What types of email you send	The nature of the business and why recipients expect these emails
Are all addresses double opt-in?	Yes, or be honest about which sources aren't

A specific answer beats a general promise. "We removed 3,100 addresses from a 2023 trade-show import and verified the remaining 18,000" tells the reviewer more than "we cleaned our list."

Step by step

1. Stop the job that sent the list so nothing queues more mail to it.
2. Export the Bounces tab of the domain's suppressions (Send > Sending > Suppressions, or the API). Each entry shows the error the receiving server returned; the bounce message analyzer sorts them into permanent and temporary.
3. Remove those addresses from your own contact store: CRM, database or CSV. Mailgun warns that removing them only from its suppressions, and not from your lists, starts the process over.
4. Verify everything that's left on the verify page and drop the invalid results. Keep risky and unknown results out of the first sends back.
5. Work out the bounce rate you'd have had with the bounce rate calculator, and include the before-and-after in the ticket.
6. Open the ticket from the Support page of the control panel with the answers in the table above.
7. Add a check at signup so new typos never reach Mailgun: Mailgun itself recommends validation at the point of signup and confirmed opt-in.

Two things that look similar

A red banner saying the account is temporarily disabled or rate limited, with a link to a business verification form, is a separate process. Mailgun uses it to lift limits such as 100 messages per hour, and you answer two forms rather than a bounce ticket. And if you suspect the bounces came from someone else using your credentials, Mailgun's first step is to rotate the SMTP credentials or API key.

What verification can't promise

It removes addresses that don't exist. It won't make a bought or scraped list acceptable to Mailgun, and it can't confirm every address: catch-all domains accept anything and some providers don't give a clear answer, so a share of results is risky or unknown. For the general recovery order after a bad send, see what to do after a high bounce rate.

Where SimpleVerifier fits

Verify the remaining list on the verify page, or call the API at signup. The first 100 checks are free with a Google sign-in. Pro is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off; API use has its own limits and isn't unlimited. See pricing.