You are invited to attend Super Service training! Please note that these sessions are mandatory. Let your manager know that you will be attending class this day.
"Mandatory." I don't know about you, but to me that sort of defeats the concept of this being an "invitation," now doesn't it? Maybe people who hold hostages in bank robberies are just severely misunderstood -- they were inviting the bank teller to a mandatory opening of the bank's vault. Invited at gunpoint, but an invite none the less.
Or, as Hank would say, "Your choice... is fish."
I love how communications and memos inside this workplace continue to string words together that are never found in the wild associating with one another of their own free will.