more errors observed on dovecot.log are:
May 18 20:34:45 dovecot: Info: Dovecot v1.2.17 starting up (core dumps disabled)
May 18 20:34:56 imap-login: Info: Login: user=<backup@mydomain.com>, method=PLAIN, rip=xxx.xxx.xxx.xxx, lip=xxx.xxx.xxx.xxx, TLS
May 18 20:34:56 dict: Info: mysql: Connected to 127.0.0.1 (iredadmin)
May 18 20:35:45 imap-login: Info: Login: user=<sonicwall@mydomain.com>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Sent/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Trash/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Drafts/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Junk/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Info: Disconnected: Logged out bytes=29/419
May 18 20:35:45 IMAP(sonicwall@mydomain.com): Error: Sending log messages too fast, throttling..
May 18 20:35:46 imap-login: Info: Login: user=<sonicwall@mydomain.com>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Sent/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Trash/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Drafts/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Junk/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: Sending log messages too fast, throttling..
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Sent/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Trash/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Drafts/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Junk/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 imap-login: Info: Login: user=<sonicwall@mydomain.com>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Sent/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Trash/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Drafts/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Junk/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:35:46 imap-login: Info: Login: user=<sonicwall@mydomain.com>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: Sending log messages too fast, throttling..
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: Sending log messages too fast, throttling..
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Info: Disconnected: Logged out bytes=70/479
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Info: Disconnected: Logged out bytes=50/453
May 18 20:35:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:35:47 IMAP(sonicwall@mydomain.com): Info: Disconnected: Logged out bytes=102/590
May 18 20:36:46 imap-login: Info: Login: user=<sonicwall@mydomain.com>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Sent/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Trash/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Drafts/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Junk/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:46 IMAP(sonicwall@mydomain.com): Error: Sending log messages too fast, throttling..
May 18 20:36:47 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:47 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:36:47 IMAP(sonicwall@mydomain.com): Info: Disconnected: Logged out bytes=140/701
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Sent/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Trash/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Drafts/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/.Junk/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:46 imap-login: Info: Login: user=<sonicwall@mydomain.com>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir_parents(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir) failed: Permission denied
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:46 IMAP(sonicwall@mydomain.com): Error: Sending log messages too fast, throttling..
May 18 20:37:47 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:47 IMAP(sonicwall@mydomain.com): Error: mkdir(/mnt/glusterfsvmail1/mydomain.com/s/o/n/sonicwall-2012.05.18.20.00.28//Maildir/cur) failed: Permission denied (euid=501(vmail) egid=501(vmail) missing +w perm: /mnt)
May 18 20:37:47 IMAP(sonicwall@mydomain.com): Info: Disconnected: Logged out bytes=140/701
please note that sonicwall@mydomain.com is ID for my SonicWall firewall E-mails. so using backup@mycomain.com id Firewall is sending emails to sonicwall@mydomain.com which is configured on XP/Thunderbird. Mail sending frequency is quite high like 100 mails per minute or near to 100.
Is it because of mail frequency is very high due to which it is not able to cope up or do I have to set something else settings to reduce the processing of such mails?