What are the operations involved when emptying a trash? I encountered this issue whereby the mailbox server timeout after a user empty a 3GB trash.

The MTA server sending to the Mailbox server receives a timeout from the mailbox server. Then, users with large mailbox size (>=3GB) on that Mailbox server are unable to login to webmail. The other users with small mailbox size on the same Mailbox server are still able to login to webmail.

Is there any optimization that can be done on the delete operation? Why are users with large mailbox are not able to login to webmail but no issue with IMAP?

Any ideas?