[NAME, COMPANY AND ADDRESS, ex.
John Smith
XYZ Inc.
1234 First Street
Suite 567
Anycity, Anystate  85245] 

Dear [NAME, ex. John Smith],

I am writing to you with some information I believe will interest you.  [STATE PROMOTION, ex. To promote our Magnaflux compressors, we will be offering a 20% discount during June 15 to 20.]  I thought you would be pleased to have advanced notice of this promotion. 

If I may be of any assistance, do not hesitate to call me at XXX-XXXX.

Sincerely, 

[YOUR NAME, ex. Jill Jones]