[Exim] connection refused

I'm having a connection refused error message with some of my outgoing mail. Apparently the problem is with only one mail server from spain (mail.jazztel.es). All other outgoing mail is getting thru. My question is: could that be because they reject my connection for some reason or there is any other reason related to my config? I'm using exim 4.23 set by default by cpanel.

Thanks

Robert Garrigos
CataloniaHosting