We have recently added a button-generator to SendCastle which makes it easy to create buttons using plain HTML (see below for screenshots). These buttons should work in all email clients, but be aware, they will not look *exactly* the same everywhere but they will always look like a Call-to-action (this is the unfortunate world we live in). :)
You get to the button creator by clicking the megaphone () in the editor-toolbar, to tweak a button, simply double-click/tap it.
The actual dialog for modifying a button
The examples are in Dutch this time!