This is available with R80.20 Mgmt & MTA running on R80.20 GW
1) MTA Logs
Within your logs you now get Postfix logs in the GUI - just filter for blade:MTA

You can see mail queue ID and even the E-Mail headers in the log.
Also it is possible to see all logs tied to an email by setting the "Original Queue ID" as a filter:

In the sample above yoou can see that the email logged as MTA log also created a TE log.
2) MTA Monitoring
You get new Views in SmartEvent.

a) MTA Overview
General statistics about mail processing. Note that almost all graphs are clickable to drill-down to the relevant logs:


b) MTA Live Monitoring
Here you can get a live view and statistics about your MTA queue. You can even manipulate items in the Postfix queue:

c) MTA Troubleshooting
Troubleshoot errors that appeared while processing emails:

Again you can drill-down by clicking the graphs/items:

HTH
Thomas