User has over 60.000 mail’s, can’t delete anything

As mentioned in a topic opened earlier today, a customer of mine had running two cronjobs every minute, sending their output to username@hisdomain.com for the past few months. Nobody noticed, until the server crashed tonight while caching the usage quota of this user’s mailboxes. After some calculating, i’m sure there are over 60.000 email’s in the username@hisdomain.com mailbox. When I open the map and execute the command ‚ls’, I can wait until I’m death as ls can only read a directory very slow. The user has 3 mailboxes:

info@hisdomain.com
surname@hisdomain.com
username@hisdomain.com

It’s very important that I don’t delete any mail from info@hisdomain.com or surname@hisdomain.com. All the mail of username@hisdomain.com could be deleted, as this are only output mails from the cron.

I have two concrete questions about this:

  • Under the user’s folder I have a folder called /Maildir, which I can’t open. Also there is a folder /imap/domain.com/emailbox/Maildir. Is it correct that I can delete /Maildir safely without losing any email of info@hisdomain.com and surname@hisdomain.com? Will I delete only all the email of username@hisdomain.com?
  • At this moment I have 26.000 email’s in my own account. In about two years this amount should be around the 50.000. It’s clear for me now that DirectAdmin can’t handle this amount of email’s. Is their any fix or workaround to let directadmin work with this amounts of mail without crashing?

Thanks in advantage,
Marijn

Note: English is still not my native language and I know not all the spelling and grammar is correct, my apologize!