Hi Sergiy,
In SAPMEINT Global Configuration the parameter for retry is "SAPMEINT_RETRY_RETENTION_PERIOD". But does the system retry for Failed mesages? What I have seen is that it retries for the messages with "RETRY" status not for "FAILED" message. So, here I think system needs to put the messages in "RETRY" status if SAP ECC connection is not available and scheduler will retry those messages based on retry count. Because there can be other reasons for message failure like as some field value missing or incorrect data.
Thanks in Advance
Chandan