Mark
it is also available under std OPM, whilst we don't currently use it I have just tested it by sending 3 different letters to the print queue the last one set as trigger doc and this sent all 3 to the printer out of OPM without user intervention
if you have made sure the subject line on the first email starts with Ref: bb-bpyrefno - subject where bb stans for branch and bpyrefno is full policy ref eg abc01pc01 then open attach should automatically file these every half hour with out any intervention on your part including replies
We send all items to open print manager and then go on with next piece of work and print all at post time.
if you have a lot of sub documents / nested if then statements in your letter it will slow the process down as far as I know.