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

Dear [NAME, ex. John Smith], 

Congratulations on graduating from the [NAME OF PROGRAM, ex. Executive MBA Program]. I know how hard you have worked to accomplish this achievement and all the sacrifices you made along the way.

I have no doubt that the wisdom you have gained (and the new credentials) will lead you along a prosperous and rewarding career path. 

I hope to remain in touch with you.

Best regards, 

[YOUR NAME, ex. Jill Jones]