pop3 duplicate email issue

Message

An issue is occurring where people use the feature "leave a copy of this message on my email server for X number of days" in their e-mail client. If our pop3 servers for what ever reason are not available for a period of time and during this period of time your e-mail client gets an error message it's left in an inconsistent state. So to ensure that you've got all of your e-mail, it'll download the mail again.

The reason behind this issue is that our mail servers are using NFS to access the shared storage and they're leaving stale locks on files which is causing issues. We've got a temporary fix in place that can fix this in a few short seconds, however the duplicate e-mail issue can occur when this happens.

To fix this we're going to move to NFSv4, currently we're using NFSv3 which has locking issues and is generally not anywhere near as good as NFSv4. This solution has to be tested fully before we can put it live. We hope to test it in our lab over the coming days and I'll do a maintenance window to schedule a few minutes downtime for switching the live servers over.