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

Dear [NAME, ex. John Smith], 

Congratulations! I just heard the wonderful news.

I respect and admire your choice of partner and I have no doubt that the two of you will compliment one another. 

I wish you all the best in the years to come.

Best regards,
 

[YOUR NAME, ex. Jill Jones] 

PS.     You know who to call if you ever need any "words of wisdom".