Web mail
Web mail puts all Solis-mail functionality at your disposal. All you need is web browser. Web mail (OWA, for Outlook Web Access) is accessible on the web address https://solismail.uu.nl. Use your Solis-id to login.
In general
OWA offers virtually all Outlook functionality, with some limitations. E.g. you cannot open several mailboxes at the same time.
Opening another mailbox in web mail
If you have been authorized to access another mailbox, you can open this mailbox in webmail, including calendar and contacts.
Let's say you are authorized to use the mailbox for science.example@uu.nl

First, login to your own mailbox. At the top tight hand corner, you will see your own name. Click it, and in the pop-up screen, enter the name of the authorized mailbox, in this case science.example. Click 'Open' (see image at right).
You can also open the authorized mailbox directly form a URL or bookmark. For this, open the address
https://solismail.uu.nl/owa/science.example@uu.nl
Use your own Solis-id and password to login.