A person is having difficulties sending emails to me. They always receive a post master kick back message...

mcurrie@...
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:

...

What can be done to fix this issue. For whatever reason the person was placed on my block email list. However, they are still receiving this message even though they were taken off of the block list.

Please help.