Well, thanks for your reply, but this isn't the solution. The problem is that I use the Mail-app to make a connection with the Exchange-account that I use for my work. Therefore, the properties of this account are not on my computer. Therefore, when I open the control panel, this account is not present under the mail-icon.
With this App, it was the first time I could make a direct connection with my work-account. Before that, I had to use Webmail. But when I open this App, and then open the settings, I can 'see' the exchange-account but I cannot edit the settings. The only possibility I seem to have is to delete this account and create a new one, with the new password. This seems to be a bit complicated. Surely there must be a better possibility.