ipad email inbox and preview pane is useless

The tags appended to your post suggest that you have an iPad Pro (indeterminate model) with iPadOS 18 installed.

As such, given that your iPad has a larger screen, you should see the message list displayed to the left with the main message preview pane to the right. If you have enabled the Mail sidebar, you will see the sidebar to the left, the main preview pane to the right - and the message list will be between the two.

If you have updated to iPadOS 26.x, you can resize the relative panes by dragging the associated divider to the left or right as required.

If your iPad is not operating as expected, try a forced-restart - as this will often clear an isolated or post-update software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

If the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:

How to back up your iPhone, iPad, and iPod touch - Apple Support

When you are happy to proceed, you can perform the reset from iPad settings:

Settings > General > Transfer or Reset iPad > Reset > Reset All Settings

If the problem still doesn’t clear, the next step is to reset the iPad to factory settings:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Otherwise, you would be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to assist with troubleshooting:

Genius Bar Reservation and Apple Support Options - Apple

Continued...

As for the new Liquid Glass UI, some users dislike or have difficulties with the new Liquid Glass appearance.

iOS/iPadOS 26.1 introduced a new setting that subtly changes the appearance of Liquid Glass:

Settings > Display & Brightness > Liquid Glass - select Clear or Tinted

If you have difficulty with the new Liquid Glass UI, there are settings that can significantly improve the appearance and suppress the majority of unwanted effects:

1. Settings > Accessibility > [Vision] Display & Text Size > Reduce Transparency - set to ON
2. Settings > Accessibility > [Vision] Display & Text Size > Increase Contrast - set to ON
3. Settings > Accessibility > [Motion] Reduce Motion - set to ON

Each if these settings can be used individually, or in combination. Setting Reduce Transparency alone (1) will likely suppress the majority of your issues. The Reduce Motion setting (3), if used, will eliminate the "lensing" effects of the Liquid Glass UI. Experiment; you should find a combination that works for you.

I suggest that you begin with setting Reduce Transparency to ON - and then, if needed, experiment with additional use of one or more of the other options.

NB: The new Display & Brightness > Liquid Glass setting can only be changed/toggled while Reduce Transparency is set to OFF. You might find that setting Liquid Glass to Clear, prior to enabling Reduced Transparency to ON, may give the best result.

Liquid Glass is here to stay - and will likely evolve throughout the lifespan of iOS/iPadOS 26. Hopefully, Apple will provide additional controls over time with which to selectively eliminate aspects of the new UI to better meet the functional and visual needs of the wider user population. Liquid Glass is very "pretty" - but for some is arguably form over function, reducing legibility and usability for some users.

You - and anyone else that has an issue with the Liquid Glass implementation - should submit constructive comments via Apple's Product Feedback portal. For iPad:

Feedback - iPad - Apple