Problems delivering email to icloud email accounts

I'm trying to send email from my corporate exchange email server to iCloud email addresses and it comes back undeliverable. the error is as follows

 A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.
The following organization rejected your message: [].

Diagnostic information for administrators:
Generating server:
[] #<[] #5.0.0 smtp; 5.1.0 - Unknown address error 550-'5.7.0 Blocked - see' (delivery attempts: 0)> #SMTP#

I checked with proofpoint and our server is not blocked
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

timgreen7077Exchange EngineerCommented:
the error indicates that the address is unknown. verify the email address is a accurate and misspelled or anything
primetime24Author Commented:
I've tried with my personal icloud email address and have gotten the same results
primetime24Author Commented:
It's not exclusive to any one icloud email address, It's any email address affiliated with icloud
timgreen7077Exchange EngineerCommented:
if it happens on any iCloud account and it seems proofpoint is your smarthost, you may need to contact them and inform them of that.

before doing that send a test email to your iCloud account from gmail or something and see if successful. if it fails that also then there may be a issue with iCloud accounts or something at the moment, but if successful, contact proofpoint and inform them.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
timgreen7077Exchange EngineerCommented:
Recommended author looks at proofpoint support for solution, since only icloud accounts are affected. closing ticket unless author reopens requiring further assistance.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.