make Mail Subject line [_time] show hh:ii:ss (seconds) instead of just hh:mm

the mail tag for the subject line has a [_time] value, but only shows the hh:ii format (hour/minute) and does not include the seconds.

Justification for use: I need/want unique subject lines, and adding the timestamp to the subject ALMOST resolves this, except when 2 forms are submitted during the same minute, causing them to have the same identical subject line since only the minute is show in timestamp and not the seconds.

the _format doesnt work for tags in the mail section, so looking at other options? or is there another unique ID i could use?