Yes, in case somebody stays few hours next to a cam, you'll get so many E mails that your ISP will reject your mails for about 24hrs. Then if you leave your house you're not protected anymore.
It's a happy middle between sensitivity of detection, mail rejection risk (then no protection), home being empty or not.
It should be a value between 1 to 10 minutes (like 1, 2, 3, 5, 10).
I used this parameter with my previous cams (with 5 minutes) and never got rejected since I used it.
With my 4 new DCS932L and sensitivity at 5%, I have this issue.
In addition, when one cam is sending too many mails, every cam of the same type (or may be Brandt) is being rejected by my ISP (using same E mail address or different ones). When one of my 4 DCS932L is sending too many mails, my 4 DCS932L are being rejected, but not my old cams.
Thanks