Undelivered Mail Returned to Sender

This is the mail system at host client-cyclone.me.

I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

I getting this issue while I sending mail…
If anybody know, how to solve this issue, please help me.

You got the same issue i got, just backwards.
I can send, but not receive.

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