Thanks for the link wharvey, but I didn't (specifically) find my answer (perhaps I completey missed it).

My question is in regards to font type, not font size. When I changed my signature last Sept, I chose "Palatino Linotype" as the font--and it worked. But if I try to change my signature now, I am unable to change the font.

Based upon the date of the thread you referenced, I assume that when font size regulations changed, so did font type regulations--but that is not explicty made clear.