We've now changed the default sort order in the web interface to the received date of the email.

Previously we were always sorting by the "Sent date", which is the date that appears in the "Date" header of emails. We're now sorting by "Received date", which is the date the message was actually delivered into our IMAP store. The only exception is the Sent Items folder, which uses the Sent date (Date header) by default.

You can also change the default sort used on the Folders screen now, there's an extra "Def Sort" column with 4 options: Recv, Recv (reverse), Sent, Sent (reverse) should you want the old behaviour.

The reasons for this change are:

  1. Almost all IMAP clients (Outlook Express, Thunderbird, etc) use the
    received date for sorting by default, so there were times when the
    web interface and users email clients were showing inconsistent
    message lists causing people confusion
  2. If you sort by sent date, then if an email is delayed for some
    reason in transit (eg slow forwarding server, held in a POP store
    for a while before being retrieved), then when it arrives it may be
    sorted below other emails that were received in the meantime. This
    might cause people to miss the email
  3. Similarly, some clients/systems with a bad clock may send an email
    with a date far in the past/future, again causing the email to be
    stuck at the top/bottom of the message list
  4. Because of the way the imap server works, sorting by received date
    only requires accessing the the servers "index" file and not the
    larger "cache" file. This should make switching between large
    folders in the web interface noticeably quicker

For further discussion of this change, please see the this forum thread: