emails are going fine from all mailboxes to one gentleman except from SMTP relay server.

This occurs from any machine (I’ve tested both from my Workstation in Woking, and from several machines in the 172.24.72.* IP range)

Remote host said: 550 5.7.1 Service unavailable; Client host [] blocked using FBLW15; To request removal from this list please forward this message to

Discussion between MS and someone with a similar issue can be found here:
So we probably just need to email quoting the IP
… but I don’t know what CC policies are on that / whether it’s appropriate for me to do; I would have through that would be the MDS action to resolve issues such as this one?

can you help find the cause
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Will SzymkowskiSenior Solution ArchitectCommented:
Yes you would have to email them to remove you from their blacklist.

pramod1Author Commented:
remove who ? I didn't get it and why this is happening?
Will SzymkowskiSenior Solution ArchitectCommented:

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