We have migrated to zimbra all our mailboxes. The problem is that webmail shows wrong date in messages. The date is the exact day when we migrated the mailbox. Inside the message the date is ok.

At the client (Thunderbird/Outlook), it downloads all the messages again, having duplicated mails at the computer.

How can we avoid downloading again all the mails? We have mailboxes with thousands of mails.-.....