They need a graphic/text/hyperlink signature for their Outlook emails. The signature must not “break” under general reply conditions from addressees.
The real problem, therefore, is to obtain a list of mail clients that my client’s clients use (Outlook, Thunderbird, web-based gMail etc) and build a signature that doesn’t break under regular conditions.
So we also need to define “regular”.
Any work done on my part to build a signature without knowing the boundary conditions is doomed to be a disaster, because the client’s client is finicky, my client has told me so, and they will leap at any chance to declare my efforts worthless when they fail in a previously-undisclosed mail client.
This is a time for me to dig in my heels and hold fast, insisting that the client’s client themselves declare a list of mail clients.
It is a necessary but unpleasant part of my job,