I often read the phrase ‘above-mentioned’ in an email or letter when someone wants to refer to what has been written in the subject line or heading. But we really don’t need it today. Instead of using this old-fashioned phrase, we can just write, “above” or “this/these”.
So let’s say you’ve written the following text in your subject line: “Presentation seminar on 24 August 2014”. You could start your email by writing: “Thank you for registering for the above seminar”. Or just write: “Thank you for registering for this seminar”.
I think that’s clear enough, don’t you? Everyone will know what you mean!