When attempting to delete an email forwarder, the "Forwarders" interface doesn't show a success or failure message. Entries similar to the following are generated in the cPanel error_log file.
[2022-12-01 01:25:44 -0500] warn [cpanel] (XID a85ywe) The system failed to write 53.21 KB to a file handle because of a
n error: Disk quota exceeded
[2022-12-01 01:25:44 -0500] warn [cpanel] Failed to save cache to /home/cpaneluser/.cpanel/datastore/AVAILABLE_APPLICATIONS_
CACHE_en_jupiter: Cpanel::Exception::IO::WriteError/(XID 7mzx32) The system failed to write 35.18 KB to a file handle be
cause of an error: Disk quota exceeded
When an account is over its disk quota, cPanel cannot create the temporary files needed to modify the forwarders. However, there is no feedback in the "Forwarders" interface indicating that an issue was encountered.
We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-41965. Follow this article to receive an email notification when a solution is published in the product.
Increase the account's disk quota, then delete the forwarder.