When you try to add an approved sender, you get the following error message:
The custom form could not be opened. Outlook will use an Outlook form instead. There is not enough disk space to copy the form to your computer. Close some forms, or increase the maximum space for forms using the Options command on the Tools menu.
The issue occurs when the temporary storage for your forms has reached its limit. To resolve the issue, adjust the limit to a higher value by doing the following:
- Open Outlook.
- Click Tools > Options.
- Go to the Other tab, and then click Advanced Options in the General section.
- Click Custom Forms, and then adjust the value in the Temporary storage for forms section. This is set to 2048 kilobytes by default.
- Click OK and then restart your computer.