Kindly help as this is frustrating:
Exception:

com.zimbra.common.service.ServiceException: system failure: Synchronization of folder '[Gmail]/Sent Mail' failed
ExceptionId:mid=8:1236548302627:7ab7195778c0f888
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE (ServiceException.java:253)
at com.zimbra.cs.datasource.ImapSync.syncFailed(ImapS ync.java:291)
at com.zimbra.cs.datasource.ImapSync.syncRemoteFolder s(ImapSync.java:214)
at com.zimbra.cs.datasource.ImapSync.syncFolders(Imap Sync.java:186)
at com.zimbra.cs.datasource.ImapSync.importData(ImapS ync.java:145)
at com.zimbra.cs.offline.OfflineImport.importData(Off lineImport.java:88)
at com.zimbra.cs.offline.GMailImport.importData(GMail Import.java:49)
at com.zimbra.cs.datasource.DataSourceManager.importD ata(DataSourceManager.java:154)
at com.zimbra.cs.mailbox.LocalMailbox.importData(Loca lMailbox.java:417)
at com.zimbra.cs.mailbox.LocalMailbox.syncAllLocalDat aSources(LocalMailbox.java:389)
at com.zimbra.cs.mailbox.LocalMailbox.sync(LocalMailb ox.java:431)
at com.zimbra.cs.mailbox.LocalMailbox.syncOnTimer(Loc alMailbox.java:361)
at com.zimbra.cs.mailbox.DesktopMailbox$1.run(Desktop Mailbox.java:436)
at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)
Caused by: com.zimbra.common.service.ServiceException: system failure: Unable to store IMAP message data
ExceptionId:mid=8:1236548302620:7ab7195778c0f888
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE (ServiceException.java:253)
at com.zimbra.cs.db.DbImapFolder.createImapFolder(DbI mapFolder.java:111)
at com.zimbra.cs.account.DataSource.createImapFolder( DataSource.java:320)
at com.zimbra.cs.datasource.ImapSync.createFolderTrac ker(ImapSync.java:83)
at com.zimbra.cs.datasource.ImapFolderSync.createLoca lFolder(ImapFolderSync.java:524)
at com.zimbra.cs.datasource.ImapFolderSync.syncFolder (ImapFolderSync.java:129)
at com.zimbra.cs.datasource.ImapSync.syncRemoteFolder s(ImapSync.java:209)
... 12 more
Caused by: java.sql.SQLException: The statement was aborted because it would have caused a duplicate key value in a unique or primary key constraint or unique index identified by 'SQL090308184003900' defined on 'IMAP_FOLDER'.
at org.apache.derby.impl.jdbc.SQLExceptionFactory.get SQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.generateCsSQLExcep tion(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl .wrapInSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl .handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.handleE xception(Unknown Source)
at org.apache.derby.impl.jdbc.ConnectionChild.handleE xception(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedStatement.executeS tatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement. executeStatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement. executeUpdate(Unknown Source)
at org.apache.commons.dbcp.DelegatingPreparedStatemen t.executeUpdate(DelegatingPreparedStatement.java:2 33)
at com.zimbra.cs.db.DbImapFolder.createImapFolder(DbI mapFolder.java:106)
... 17 more
Caused by: ERROR 23505: The statement was aborted because it would have caused a duplicate key value in a unique or primary key constraint or unique index identified by 'SQL090308184003900' defined on 'IMAP_FOLDER'.
at org.apache.derby.iapi.error.StandardException.newE xception(Unknown Source)
at org.apache.derby.impl.sql.execute.IndexChanger.ins ertAndCheckDups(Unknown Source)
at org.apache.derby.impl.sql.execute.IndexChanger.doI nsert(Unknown Source)
at org.apache.derby.impl.sql.execute.IndexChanger.ins ert(Unknown Source)
at org.apache.derby.impl.sql.execute.IndexSetChanger. insert(Unknown Source)
at org.apache.derby.impl.sql.execute.RowChangerImpl.i nsertRow(Unknown Source)
at org.apache.derby.impl.sql.execute.InsertResultSet. normalInsertCore(Unknown Source)
at org.apache.derby.impl.sql.execute.InsertResultSet. open(Unknown Source)
at org.apache.derby.impl.sql.GenericPreparedStatement .execute(Unknown Source)
... 22 more

If issue persists please post description and debug information here.