Log in to the Mirth Interface Engine. From the Dashboard, double click on the channel with errors. Select a Date Range that includes the errored messages. Under the Status dropdown, select ERROR and click the Search button:
Select the Reprocess Results button to re-send all results from the current search you did above:
Click the check mark next to Overwrite existing messages and update statistics and then click OK:
If you only want to reprocess one message and not a batch you would just select one message and then click the Reprocess Message button.