I have the same problem with all outlook and office365 in the 120dpi version. The text in the button is always in two lines (content is two small words) and since the height does not adjust, the text is cut off. I use the button in a 100% column, for example.
I have tried to use but your button field does not allow hmtl content. If i set the button to full width there is no line break, but in the mentioned clients it does not go to 100 % width either, but it is wider than the button value.
Acymailing is up to date.