Within the Hosting email, you have the option to send messages to a mailbox other than the one you are currently logged in to. To do this, you can set up a profile in Webmail, through which you can then send a message as another mailbox. The option to set up a Profile can be found in Settings, where you can create a new profile, see picture.
You can then select a profile when writing a new message in the Sender field:
The option to send emails for another mailbox can only be used within your domain, e.g. for info@yourdomain.eu you can create a profile for admin@yourdomain.eu but you will not be able to send a message from admin@anotherdomain.com