Mailing list and time to time error: MX or domain found

#1

Hello!

From time to time I send letters to my colleagues, using a specialized service for mass mailing of e-mail.

On average, I send letters to 250-300 recipients. After about two-hundredth user, some emails are not sent with an error:

MX: no MX RESP: 5.1.3 MX or domain found
Unrouteable address

When you resend – emails are not sent for some time. Apparently blocked. I use DNS cloudflare.com. What could be the problem? cloudflare.com has a limit on the count of requests per time unit? How to avoid?

#2

I’m not sure how this is related to what DNS you use. The specialized service is what should be doing the MX lookups so they deliver the mail. Have you contacted them about this issue?

#3

Thank you for answer. Yes, and they said me about error in them log:

MX: no MX RESP: 5.1.3 MX or domain found
Unrouteable address

#4

Post screenshots of the error and the configuration where you configured the mail servers.

#5

Asking the provider.