I'm using Mac Mail v 5.1 (Lion) as a mail client, and I and have configured Zoho mail over IMAP. It seems as though Mac Mail issues a COPY command when moving a message to a mailbox configured via IMAP. If so, changing the date to the current date is inconsistent with the IMAP specification, which recommends that the date of the source message be preserved. Regardless, this behavior is inconsistent with other mail services. Moreover, it's not behavior that I would expect when moving messages among mailboxes.