Gets the maximum message number limit for the account or folder the quota applies to.
The non-negative Int32 value containing the maximum message number limit for the account or folder the quota applies to, or -1 if this information is not available.
Nowadays, most servers limit maximum storage size only (maximum number of messages is not limited). Due to this, CurrentMessageCount and MaxMessageCount properties usually return -1.
FolderQuota Class | MailBee.ImapMail Namespace