To be able to customize the Out of Office message, and have it the same across clients

The customer would like to be able to fully customize the wording of the Out-of-Office (ooo) message, as they feel that the current wording is not clear as to what is the last day of absence and what is the date the user will actually be back in (return to) the office.

E.g they are based on Poland and normally an ooo message would include the last day of absence, rather than the return date for example:

I would like to kindly inform you that on days: <date from> - <deadline to> I stay outside the office.
<date from>: first day of absence
<date to>: last day of absence (not yet at work)
in the wording: "I am not at work from 26/02/2019 and I will not be back before 05/03/2019." the phrase is imprecise. It is not known whether on 05/03/2019 the user will be at work or if this is the last day of absence.
We need two fields :
* <date from>: the first day of absence
* <date to>: the last day of absence (not yet at work)

They would also like the message to be the same across clients as currently there is a slight wording difference depending on where the ooo message is set.