Tried sending an email yesterday and got the following error message:

SMTP error from remote mail server after initial connection:
554-in.ip16nec.int.opaltelecom.net
554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.

Only happened on sending to one client who is on Talk Talk. Quite strange as there's an ongoing email conversation between us and now my relplies don't get through. I've had a google of it and it's as clear as mud!

Any of the Techy crew like to explain in actual English what this means and the course of action I need to take.

Thanks in advance