请问一下，以下错误怎么会产生，谢谢！
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Error: read(/var/run/dovecot/dict-server) failed: Remote disconnected
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更多的dovecot错误日志：
[root@imail log]# dovecot --version
1.1.18

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dovecot: Aug 17 10:35:31 Error: dict: db_env(): Unable to allocate memory for transaction detail
dovecot: Aug 17 10:35:31 Error: dict: db_env.txn_begin() failed: Cannot allocate memory
dovecot: Aug 17 10:35:31 Error: dict:
dovecot: Aug 17 10:35:31 Error: dict: db(/var/lib/dovecot/expire/expire.db) open failed
dovecot: Aug 17 10:35:31 Error: dict: Failed to initialize dictionary 'expire'