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554 5.4.0 error when sender tries to send to a recipient in our company using office 365 hosted exchange

One of our clients is using Office 365 hosted Exchange.  One user has a customer of theirs who gets a 554 5.4.0 error when trying to send email to this one user on our customer's O365 domain.  Anything I can do to get O365 to accept email from this sender (ignore too many hops error)?

Thank you,

John S.

Answer
Answer
Simply whitelisting the sender's domain in the spam filter in Exchange admin section of O365 corrected the problem.  I was surprised because the error, which refers to "too many hops" detected in the headers, is not a classic indicator of spam, such as falsified information in the header.  Exchange blocks this message under suspicion of spam, but it is less definitive as other indicators, so I thought I was going to have to take further measures.  The error really refers to the config on the sender's side, and I was concerned that it could not be rectified on the recipient side.  Anyway, all that worry for nothing, whitelisting in the O365 spam filter did the trick.  Thank you for your response.  This issue has been resolved.

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Question Info

Last updated April 13, 2025 Views 72,825 Applies to: