First FAQ: "Why am I receiving unwanted e-mail from my LiveJournal address?"
Due to the nature of e-mail, it is not possible for LiveJournal to control who uses any given address as the "From" address on e-mail messages.
It is possible for people to forge the "From" address on e-mail messages to make it appear as if it is your e-mail address that is sending unwanted messages. The @livejournal.com e-mail address is intended for use as a forwarding service only, and sending e-mail using it, while possible, is not supported by LiveJournal.
As such, LiveJournal cannot take any action on reports of spam or other unwanted e-mail with @livejournal.com return addresses. You may wish to contact your e-mail provider to determine what spam filters are made available for your use, but you may also wish to whitelist email@example.com and firstname.lastname@example.org to ensure that you do not inadvertently block LiveJournal notification messages. Additionally, you may want to whitelist 22.214.171.124 and 126.96.36.199 (the IP addresses used to send comment notifications and forward email@example.com email).
Second, I'd like to edit FAQ 115 to include a section regarding: "Why can I only receive some mail from LiveJournal?"
Perhaps at the end we can say "Because notifications, other messages from LiveJournal, and e-mails forwarded through your firstname.lastname@example.org address are all sent through different servers and from different addresses, you may be able to receive some of these messages but not others. If this is the case, please make sure that you have edited your spam filters completely as discussed above, and contact your email service provider if the problem persists."