OUTLOOK modifying PDF files as attachments

I am using Office 2003 SP2. Outlook has suddenly decided to turn all my PDF attachment files into zip files when sending them out -> I attach xxxx.pdf and when sent the file becomes xxxx.pdf.zip. Don't know what is going on or how to change it back. Any suggestions appreciated. I was so desperated I resorted to AOL!

 

There are a few outlook add-ins which automatically compress outgoing attachments, these can be checked in Tools -> Options -> Other -> Advanced (Options) -> COM Add-Ins and .. -> Add-In Manager. Look for addins like autozip.
Otherwise:
Is this only happening to pdf attachments?
Are they actually compressed, or just renamed?

 

zipped PDF files

I checked my addon's - no autozip. Just Backup.

The mystery actually goes a little deeper. Some pdf files it does not zip. The one it does zip is 121K and zips to 106K. Other smaller files don't get zipped. I am going to try a very large file that I have sent in the past with no problem. Seems to happen only on PDF files but since they are 99% of my sendings not surprise. I will try a big DOC file to see what happens.

I am suspicious that one of MS security updates has decided to scan and zip certain outgoing files. However I suspect a lot of other people would be screaming.

I am using zone alarm suite but it doesn't seem to be in play.
Thanks for any help.

 

I checked with other files...

it seems to zip any large file whether pdf or ppt or doc.

 

Cancel the alarm --- Thanks for your help. I found my old quick view plus had added an autozip to outlook. Thanks for help!