I have a month to month verbal rental agreement after my lease ended last year, I am mailing my letter of intent to vacate( 30 day notice) today.
Need I send it registered or certified mail, confused to which one I need to use.
Thanks

I would use priority mail with delivery confirmation. It's cheaper.

I ended up doing certified mail. I can track the progress online and i see it was attempted to be delivered on the 29th (which gives a 31 day notice on my part)
She hasn't bothered to pick up the letter at the post office.
I have the certified mail slip from the PO, and I printed out the status of the tracking number that says it was attemted to be delivered
we called her originally to give her a heads up, but she has not responded, and has not picked up my intent to vacate notice.

That being said, with me living in MA, and her living in Southern California, what more can I possibly do to cover my a*s here?

really hoping someone can help- she still hasn't picked it up

Have you tried calling and telling your landlord that you've sent her your 30-Day Notice via Certified mail? Or is the issue that you suspect your landlord already knows & is just trying to avoid getting your "official" notice so she doesn't have to deal with the hassle of replacing you as a tenant?

Although I'm much more well-versed on California tenant law, it would seem to reason that as long as you have proof of your good-faith attempt to notify your landlord, whether or not she chooses to avoid dealing with it is a moot point. You've fulfilled your end of the rental contract by notifying her - if she wants to bury her head in the sand, I can't imagine that you'd be held accountable for it.

You have done all you can. Now clean your apartment and take plenty of pictures on the way out. Make sure you get behind the refrigerator, the stove inside and out, your windows and panes. Do not leave anything behind your landlord can use. Most of the time landlords have no use for it and will charge you for having to get rid of it.