These buttons only have icons on them. Yes, most of us know what the icons mean, but you are potentially degrading experience for users of screen readers.
Additionally, the "send email" button looks very similar to other buttons on the "Home" screen. You could be confusing your users. Causing them some agony by opening an email client they never use, or worse, creating a draft in their web mail when they were simply trying to understand what the button does.
They need tooltips to help make their intentions perfectly clear. Especially since all of them take you to a third party tool.