@Flikeufro87
This space is reserved for advertising on Swisscom Webmail (Bluewin), and the fact that it's white seems to indicate that an ad blocker is being used (Adblock, other...).
But you can use the native Mail App on your mobile, tablet or PC/Apple computer to check your mail. Then you won't have that half-page ad. On a computer, you can install Thunderbird (free) or Outlook (subscription) or another external e-mail solution. And you can store messages locally in folders you've created. There's no size limit, except for the memory capacity of your devices. You can synchronize your e-mails on all your devices using the IMAP protocol.
If you insist on using Swisscom Webmail (Bluewin), you can pay a subscription fee of 1.90 / month to have the advertising removed from the top of the screen.
For further information, see this page
Bluewin e-mail: New products – Help | Swisscom