[Dovecot] pop3 migration

[TeTeHacko]

Hi,
I have problems with pop3 migration, the server disconect the dovesync when
fetching mails after 5 minutes with this error in server log:

xx.xx.xx.xx   [28F4] 11:54:05 <<< RETR 6548
xx.xx.xx.xx   [28F4] 11:54:05 >>> +OK 47522 octets
xx.xx.xx.xx   [28F4] 11:54:05 <<< RETR 6549
xx.xx.xx.xx   [28F4] 11:54:05 >>> +OK 355289 octets
xx.xx.xx.xx   [28F4] 11:54:05 <<< RETR 6550
xx.xx.xx.xx   [28F4] 11:54:05 >>> +OK 9638 octets
xx.xx.xx.xx   [28F4] 11:54:05 <<< RETR 6551
xx.xx.xx.xx   [28F4] 11:54:05 >>> +OK 2188 octets
xx.xx.xx.xx   [28F4] 11:59:05 >>> -ERR Command unrecognized: ""
xx.xx.xx.xx   [28F4] 11:59:05 *** <info at istan.cz> 6551 477693894 00:12:55 ERROR
xx.xx.xx.xx   [28F4] 11:59:05 Disconnected

and this in dovecot log:

dsync(info at istan.cz): Debug: imapc(mail.stable.cz:143): Authenticated successfully
dsync(info at istan.cz): Debug: pop3c(mail.stable.cz): Looking up IP address
dsync(info at istan.cz): Debug: pop3c(mail.stable.cz): Connecting to 88.86.120.212:110
dsync(info at istan.cz): Debug: pop3c(mail.stable.cz): Authenticating as info at istan.cz
dsync(info at istan.cz): Error: pop3c(mail.stable.cz): Server disconnected unexpectedly
dsync(info at istan.cz): Error: pop3_migration: Failed to get header for msg 1:
Disconnected
dsync(info at istan.cz): Error: pop3_migration: Failed to get header for msg 2:
Disconnected
dsync(info at istan.cz): Error: pop3_migration: Failed to get header for msg 3:
Disconnected
dsync(info at istan.cz): Error: pop3_migration: Failed to get header for msg 4:
Disconnected

is there any timeout in dovecot for 300s? can anybody point me where may be some
problem? This error occurs everytime i test it and the mail box has cca 2GB, on
small mailboxes is no problem, i try this patch:
http://hg.dovecot.org/dovecot-2.1/rev/ab6a4455b27d on dovecot version 2.1.7 but
the problem isn't solved.

Thanks for help
Tomas Herceg