I cannot see any sense in the Email button before there is an empirical study on its success. For Open Access this button has the same status as Interlibrary Loan (with the difference that ILL is more successful than the button). We have interlibrary loan so we need no Open Access?
On September 7 I received 6 confirmation mails from the Zurich repository ZORA which has a similar button for a part of the non-OA items. On September 8 I received one PDF - seven days later I can say that 5 of 6 authors didn't fulfill the request. If you cannot bring harder facts this seems me enough empirical proof that the button doesn't work. Professor Harnard, maybe it would be a great idea to suggest a sample letter in English with bootlicking words for those who request but who are not known to the author. Dr. Klaus Graf
