I'm not exactly sure what you mean...you bounce messages, not senders. Unless you somehow managed to set up a rule to automatically bounce mail from a specific person (which is somewhat complicated to do), you should receive mail from them unless you manually bounce each message.
Are their messages being diverted to your Junk mailbox? If so, just flag them as "Not Junk" and Mail will quickly learn to not junk messages from them. If the messages truly aren't getting through, I'd say that your ISP possibly flagged their domain as a spam generator. That's not due to you bouncing their messages, and you'd have to petition your ISP to have the sender's address or domain removed from their blacklist.
I bounced one of their messages, and I thought that once you bounce an email address it bounces any later emails.
Since it appears this is not the case, I wont worry about it.
I bounced one of their messages, and I thought that once you bounce an email address it bounces any later emails.
Since it appears this is not the case, I wont worry about it.