InsaneJournal Announcements

I don't mean to question this, but I'm just confused. What I don't understand about this being a result of e-mail providers seeing messages as spam is that I use the same gmail account for four different journals. One journal is receiving NO notifications at all (and this is consistently so), one receives them if they're posted to the journal itself but not to comments posted elsewhere, and the other two have just spotty notifications. Why would it be so consistently different between journals?