In the process of transferring an account from elsewhere to my Cyberpanel server I ran into this email issue.
1). I created the email accounts through the panel in the normal way.
2). I transferred email files into the appropriate folders under (/home/vmail/domain.tld)
3). checked through webmail and everything worked as expected.
BUT the accounts were NOT receiving new email.
The bizarre issue was that I had cut-n-pasted the email account information from a list – RMcdonald@example.com and CP had used the capitalization in creating the account in the database and vmail folder
the new mail was being delivered to other folders e.g. rmcdonald with no capitalization. Webmail was accessing the folders with capitalization.
This could not be fixed with PHhpMyadmin…to many dependencies.
I was able to fix it by…
1). moveing the new mail from the “new” under rmcdonald folder to “new” under RMcdonald.
2). delete the rmcdonald folder and rename the RMcdonald to lower case.
3). delete the email account through CyberPanel (note: deleting the account from the panel only changed the database…the email folders all remained on disk).
4). recreate the email accounts in all lowercase.
After this the email accounts contained all transferred data and was receiving new mail.