Symptoms
The /var/log/maillog file on qmail servers contains the error messages "Created dotlock file's timestamp is different than current time" generated by dovecot, e.g.:
Aug 1 17:04:41 qmail01 dovecot: IMAP(johndoe@customer.com): Created dotlock file's timestamp is different than current time (1375394718 vs 1375394681): /usr/local/qmail/shared/mailnames/c/h/-1078/1078//Maildir/.personal contacts/dovecot-uidlist
Aug 1 17:05:40 qmail02 dovecot: deliver(johndoe@customer.com): Created dotlock file's timestamp is different than current time (1375394778 vs 1375394740): /usr/local/qmail/shared/mailnames/p/g/-292/292//Maildir/dovecot-uidlist
Cause
Time is not synced on servers in the POA-managed clustered qmail installation:
- qmail servers (MTA, Mail Transfer Agent)
- NFS server where mailboxes are stored
If clock difference between qmail servers and NFS shared storage server is more that 1 second, dovecot will generate alerts.
Resolution
Configure time synchronization between all servers in the POA-managed clustered qmail installation:
- qmail servers
- NFS shared storage server
Use NTP (Network Time Protocol) to synchronize time between qmail cluster members and NFS shared storage server:
- Install the 'ntp' package on all servers listed above
- Configure the 'ntpd' daemon to set and maintain the system time
Refer to the man pages on the 'ntpd' daemon and to the official NTP documentation for instructions how to set up time synchronization.
Refer to the Dovecot official documentation and mailing list for more details about the problem.