[Dovecot] Dovecot Hangs while mutile users download mail for same account using pop3

Hello,

I have a weird problem in dovecot, Dovecot Hangs while multiple users download mail for same account using pop3

Three persons use 1 same email , and three of them use outlook express to check That specific mail .. Also some times one of the three users check the mail for this Account using imap (squirrel mail)

And here comes the problem. suddenly all the three users are unable to check the mail And when the outlook express connect to the pop3 server, they are unable to disconnect And the outlook express keep asking "the server is not responding for 60 mins would you like to wait ?

i checked /var/log/maillog, i can see the following errors

dovecot: pop3(sales): Disconnected: Storage error during logout.

to=sales@domain.com, orig_to=, relay=local, delay=357, delays=338/0.01/0/19, dsn=4.2.0, status=deferred (cannot update mailbox /var/mail/sales for user sales. unable to lock for exclusive access: Resource temporarily unavailable)

When i used lsof | grep sales pop3 4278 sales 10u REG 8,3 22897673
12615705 /var/spool/mail/sales

i went to /home/sales/mail/.imap/INBOX , but i didnot find any lock files

-rw------- 1 sales sales 944 Oct 7 13:35 dovecot.index -rw------- 1 sales sales 49152 Oct 7 16:57 dovecot.index.cache -rw------- 1 sales sales 14044 Oct 7 16:57 dovecot.index.log

1- So what is exactly the problem? is the problem that three users are checking the same exact mail ? 2- is the problem that 2 users checking mail using pop3 and the third one checking it using imap insame time ? 3- is dovecot locking the inbox file while one of the users getting the mail ? 4- What is the cause of the problem ?

Please help Regards

Robert JR