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Dear sir/madam:
On [date], we will host an evening of celebration in honor of the retirement of [name], President of [company]. You are cordially invited to attend the celebration at [hotel], [location], on [date] from to p.m.
[name] has been the President of [company] since [year]. During this period, [company] expanded its business from to . Now it's our opportunity to thank him for his years of exemplary leadership and wish him well for a happy retirement. Please join us to say Good-bye to [name].
See you on [date].
Yours sincerely [name] [title]