BizTalk senport error

Hi,

while i am sending messages from dynamic sendport SMTP to trigger mails for 6 messages. 5 messages are triggering but 6th is the combination of all email addresses and not able to trigger. i am getting the below error

ExceptionType : Error
Exception Message :Failed while attempting to send message 'sendEmailMessage'.
at Microsoft.BizTalk.XLANGs.BTXEngine.BTXXlangStore.WriteMessageState(IBTPEPInfoLookup pepLookup, Guid portId, XLANGMessage msg, Segment seg, String opname, String url, IList promoteProps, Boolean track, IList toPromote)
at Microsoft.BizTalk.XLANGs.BTXEngine.BTXLogicalPortBinding.SendMessage(XLANGMessage msg, XlangStore store, Segment seg, OperationInfo op, IList additionalProps, IList toPromote, Boolean ignoreRoutingFailure)
at Microsoft.BizTalk.XLANGs.BTXEngine.BTXPortBase.SendMessage(Int32 iOperation, XLANGMessage msg, Correlation[] initCorrelations, Correlation[] followCorrelations, Context cxt, Segment seg, ActivityFlags flags)
at ............................segment2(StopConditions stopOn)
at Microsoft.XLANGs.Core.SegmentScheduler.RunASegment(Segment s, StopConditions stopCond, Exception& exp)