When trading on-MTF EDM/IDM values must be populated in the outbound quotes and any resultant ExecutionReport messages. For on-MTF requests here is a summary of the various Venue's behaviour:
Current UAT:
FYI for the future:
8=FIX.4.4|9=0302|35=b|49=BLP|56=MFMA_RFS|34=7|52=20191002-10:12:00|300=8|301=0|131=BLP.RFQ.800254719_MFTA|117=S1570011120.46998|297=5|58=Failed to convert to GPI, ShortCode=Dmitry_xxx DealCode=MFMA roletype=makerExecId DEAL_CODE: MFMA FIX_SESSION: MFMA_RFSQuoteReqId=BLP.RFQ.800254719_MFTA quoteId=S1570011120.46998 |10=202|
(Dmitry_002 was the correct EDM value in this case). We will convert this rejection into a QuoteResponse and forward the error message as-is.
Also, at the risk of me stating the obvious, these details are required on-MTF only - if OFF, or testing SEF then, again any values you provide will be ignored.