Hi,

I'm running 3 Dovecot director and 6 Dovecot backend on CentOS 6 and Dovecot 2.3.10, with Maildir shared on NFSv3 (on NetApp).

Since CentOS 6 will be EOL on November I started to upgrade to CentOS 7 the first Dovecot backend.

But after Director start to direct users on new CentOS 7 server some errors, for any users, come up, an example:

Aug 21 14:56:41 Error: imap(alessio@cecchi.it) session=<11sBlmKtj1qelGW/>: Mailbox INBOX: Broken or unexpectedly changed file /home/vmail/domains/cecchi.it/alessio/Maildir/dovecot-uidlist line 18664: Invalid data:  - re-reading from beginning
Aug 21 14:56:41 Error: imap(alessio@cecchi.it) session=<11sBlmKtj1qelGW/>: Mailbox INBOX: Broken file /home/vmail/domains/cecchi.it/alessio/Maildir/dovecot-uidlist line 18664: Invalid data:

Consequently to the error the user see the synchronization of his mailbox again.

The Dovecot version and configuration is the same that in CentOS 6, also the mount parameters are the same, so I suspect that could be some difference in the NFS client implementation on CentOS 7.

This the entry on fstab:

192.168.1.2:/vmail0 /mnt/vmail0 nfs rw,nfsvers=3,noatime,nodiratime,_netdev,nordirplus    0    0
# Bind for vmail0
/mnt/vmail0/domains /home/vmail/domains none x-systemd.requires=/mnt/vmail0,x-systemd.automount,bind 0 0

In the archive of this list I found a similar issue but without a solutions:

https://dovecot.org/pipermail/dovecot/2018-October/113207.html

Do you have any suggestions?
Thanks

-- 
Alessio Cecchi
Postmaster @ http://www.qboxmail.it
https://www.linkedin.com/in/alessice