message blocking in Expat

I have been blocked to send message. There are no period to lift block.
have I been blocked for ever ? I want to know when can I send messages ? if I do not know I will leave this site.

Your messages have not been blocked, you've used up your quota.

Read this

If it's the case you used up your quota, you have to delete old message threads. Meaning clean up your inbox.
You can increase  your capacity by contributing more, I.e. post more or open new threads by yourself.

when I want to send message to someone, the following message will be shown
"You can't send new private messages, as you have sent too many "copy/paste" messages. To unblock you private mailbox, we invite you to participate on the forum. Click here for more details."

That's clear enough. It's up to you how long this block contains.

How can you block people you have no interest in communicating with ?