In Webmin/Servers/Read User Mail module I can see all mail accounts on my system.
I see that when mail is in one of those accounts that there is a (xx.xx kB in 1) type of entry after the account name.
I have noticed though that even accounts that have no mail still have the KB message and that it grows larger depending on their mail volume.
Some mail account with high volume but has deleted all their mail.
highuser.example (151.03 kB in 1)
Some mail account with low volume but has deleted all their mail.
lowuser.example (10.27 kB in 1)
Is this a bug?
It is some sort of cache?
This only seems to happen with email accounts associated with virtual hosts.
mail accounts for the system such as root look like this when the account has mail:
root (5.47 kB in 1)
and then when the mail is deleted go back to looking like this:
Notice no (xx.xx kB in 1) entry.