http://www.wikihow.com/Write-a-Memo contains good information on how to right a memo. It is very similar to the purdue web-site. The only thing that it does not contain is the example of the memo.
Here is our Memo
TO: All ConAgra Employees
FROM: Matthew Everette, Public Relations Manager
DATE: October 15, 2009
SUBJECT: Salmonella Outbreak
As you all know, there was a recent outbreak of "Tennessee" strain Salmonella in the Peter Pan and Great Value peanut butters of one of our Georgia plants. This unfortunate event has given us negative attention in the media but I can assure you that we are doing everything in our power to correct this situation. The Georgia plant has been shut down and will be properly sanitized before being reopened.
We are reminding all employees that even in the face of this crisis we will stand strong. We are asking each and every one of you to continue doing your work and giving 100% of your effort. We are also reminding employees that our products go to millions of people worldwide and that these products must be made with the utmost care and concern for human life.
We also are encouraging you not to speak to anyone about our current situation. We have several members of our public relations team (including myself) working on this matter and giving the media a statement. Do not talk to anyone about this matter including friends and family.
Thank you for your patience in this matter and your continued effort.
GM Group
According to my resource, this would benefit greatly from having headings within the document. That way the memo is divided into easy to distinguish sections.
According to our source.....
1) Sender usually signs the memo using initials, first name, or complete name.
2) Very concise and direct.
KFC Komment
Clear concise and to the point. be careful with the wording due to the fact that the information can be leaked. There isn't enough information for the "Tell no one" part but it seems business like.
This follows all the rules of the source we use, it is a well written Internal Memo.
Comment
"As you all know, there was a recent outbreak of "Tennessee" strain Salmonella in the Peter Pan...."
Maybe try to make the introduction and the conclusion more formal. Word choice needs some.
Even though "Do not talk to anyone about this matter including friends and family," is important to say, it is a bit blunt. Try to work on it and say it in a bit less obvious way.