Anyone else not receiving vBulletin confirmation emails?

For months (or longer) I've been experiencing a problem that I finally need to ask about. Wondering if anyone else has experienced this.

There are numerous forums I visit for professional and personal reasons. Whenever I register for a new site that uses vBulletin for its discussion forums, I do not receive the required confirmation email if I register with my iCloud email address -- not ever, not just for one or two such sites, and they're not being filtered into Junk or another folder. If I change the account to use my Gmail address instead and resend the confirmation, it arrives instantly. There's something going on behind the scenes with iCloud that's dumping/blocking the messages before they reach me, and it's . I hate having to check a different account, since I've used iCloud since it first came out as iTools, but I don't seem to have any control over this.

Have tried contacting Apple for help but have run into a brick wall. I spent well over an hour or so chatting with a total of four different reps, leaving it with a Level 2 rep who gave me the case number and promised a reply the next day or after the weekend at the latest. That was more than two weeks ago and no reply to several email followups. The first rep I chatted with was able to replicate the problem easily, but then we got disconnected and the next rep was clueless, telling me I needed to update OS X even though I was accessing email on a Windows machine via the iCloud web interface, and then suggesting there's nothing wrong with iCloud because other email comes through okay. Level 2 rep easily replicated the issue, was able to get a sample confirmation email with complete headers, and suggested they needed to fix it at their end, but I haven't been able to get a reply from him since then. Very frustrating. At this point I'm not posting here looking for a solution but rather just seeing if anyone else has had an ongoing problem like this.