We are going to do an emergency reboot at 11pm tonight of one of our back-end mail servers.
The filing system has started to have some unusual delays. This happened to another server about a year ago and a reboot fixed it.
As this server has been up for 4 years, we suspect the same issue, so are going for the reboot option.
Apologies to all affected – outage on POP3 & IMAP for affected users should last around 10 minutes max if all goes to plan.