[Migrated from MSDN Exchange Dev] Server busy. Please try again later (S77714)

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Hi, we're an email service provider and have recently changed the IP address of one of our servers. This appears to have resulted in many emails being deferred such as this:

9631D173B8F5A 198276 Tue Nov 24 08:48:36 AAEVbZ4L2SLa1WIuIyBmdng==_1101345894578_GGSWUN9MEeKL+NSuUoRDcg==@in.constantcontact.com
(host company-com.mail.protection.outlook.com[104...] said: 452 4.5.3 Too many recipients (AS780090) [.protection.outlook.com] (in reply to RCPT TO command))
******@company1.com

This email was also originally destined for a local user on our system, but they have chosen to forward it on to their own company domain managed by Outlook/Office 365.

How can I request my IP to be whitelisted or at least verified in some way that we're not trying to spam someone?

Answer 1

Hi,
Are you sending to large number of recipients? It seems the amount of recipients for a single email has exceeded the limit. Try combining those recipients to a group and sending to that group directly instead.
If you are Not sending to large number of recipients, you might need to set up a rule for whitelist your domain/IP, follow this blog please: https://infimasec.com/support/o365-whitelist/
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

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