keep getting error message The mailbox couldn't be created on the server. how do i fix this?

Hi twbab,

We understand you're attempting to create a new mailbox in the Mail app on your iPhone.

To clarify, are you attempting to do this under an iCloud account or a different type of account? We don't need your full email address, just the part after the @. Depending on your account type and settings, you may be unable to add a mailbox in that manner.

Additionally, if you have not attempted to add the mailbox on both Wi-Fi and cellular or two different networks, we'd recommending doing so to ensure there's no network connectivity issue.

Cheers!