Too many recipients error while sending email newsletter using Mailgun

Hi, I get this error whenever I try to send newsletter. Can anybody please help me to fix this?
Capture

Have you set up a payment method in your Mailgun account?

You may get more details about the error if you look in your server side logs, there are details for how to do that in the docs:

Yes, I’ve set up payment method in Mailgun. And this is my error log

    [2019-12-09 16:24:16] WARN

    NAME: InternalServerError
    MESSAGE: The server has encountered an error.

    level: normal

    "The email service was unable to send an email batch."
    InternalServerError: The server has encountered an error.
        at new GhostError (/var/www/ghost/versions/3.1.1/core/server/lib/common/errors.js:10:26)
        at /var/www/ghost/versions/3.1.1/core/server/services/bulk-email/index.js:103:45
        at Request.callback (/var/www/ghost/versions/3.1.1/node_modules/async/dist/async.js:4617:26)
        at IncomingMessage.<anonymous> (/var/www/ghost/versions/3.1.1/node_modules/mailgun-js/lib/request.js:331:19)
        at IncomingMessage.emit (events.js:215:7)
        at IncomingMessage.EventEmitter.emit (domain.js:476:20)
        at endReadableNT (_stream_readable.js:1183:12)
        at processTicksAndRejections (internal/process/task_queues.js:80:21)

    Error: Too Many Recipients
        at IncomingMessage.<anonymous> (/var/www/ghost/versions/3.1.1/node_modules/mailgun-js/lib/request.js:327:17)
        at IncomingMessage.emit (events.js:215:7)
        at IncomingMessage.EventEmitter.emit (domain.js:476:20)
        at endReadableNT (_stream_readable.js:1183:12)
        at processTicksAndRejections (internal/process/task_queues.js:80:21)

Have you gotten to the bottom of this? Running into a similar situation with my Node.js setup.

The problem was with mailgun. Their automated system accidentally marked my account as suspicious, imposing some limit on the number of emails that can be sent from the account.
I created a support ticket and the issue was resolved after their verification.

This was the reply from Mailgun

After further review, your account was automatically placed on an evaluation period [1], which limits the account in various ways such as this. To help protect our customers against spam, we have automated systems in place to flag accounts that appear suspicious. On most occasions, this process works very well; however, sometimes we get it wrong and flag a genuine account. There are a number of factors that contribute to the flagging of the account for business verification, but they are not necessarily directly related to you.