MailBrowserControl inherits WebBrowserControl so you can use ExecWB on WebBrowserControl you can use it on MailBrowserControl
dynamic activeXInstance = mailBrowser.ActiveXInstance;
activeXInstance.ExecWB(
Exec.OLECMDID_OPTICAL_ZOOM,
ExecOpt.OLECMDEXECOPT_DONTPROMPTUSER,
150,
IntPtr.Zero);
public enum Exec
{
OLECMDID_OPTICAL_ZOOM = 63
}
public enum ExecOpt
{
OLECMDEXECOPT_DODEFAULT = 0,
OLECMDEXECOPT_PROMPTUSER = 1,
OLECMDEXECOPT_DONTPROMPTUSER = 2,
OLECMDEXECOPT_SHOWHELP = 3,
}