Email attachments

I am not able to attach files to outgoing emails and incoming emails do not have attachments. Is there some way to restore iMail to correct whatever is wrong?

 

I am using Mail on my Macbook (Os X vs. 10.5.4). My ISP is a provider I've used for years, and the problem was happening on all of my email services which all download into Mail. I am able now to make and receive attachments again, however, now a blue Lego-block icon with question marks on it appears on every email with an attachment (incoming or outgoing). I also can't see outgoing attachments on mail that I send.

Yes, I had adapted the Mail program by downloading a plug in call Mail Iconizer which is intended to help make attachments more user-friendly. Things were fine with that. However, I downloaded another program OMiC which was supposed to be able to open Office Contact files (I was trying to send myself some of my old contacts from my old PC & couldn't open the files). The OMiC didn't open the files, either, so I tried to uninstall it. After uninstalling it, the blue Lego-block icon appeared, and I've had problems with Mail ever since.

I would be happy to reload the Mail program, but don't know how, and would I lose all current emails? I haven't back up the system on Time Machine since this all occurred so that I don't back up a bad set-up.

I greatly appreciate whatever advice you may offer.