Emails not delivered, both coming and going

So for months now we have noticed that certain emails that we know were sent to our Comcast email account just never showed up.  We checked the spam folder, a junk mail folder, and anywhere else we could find that we thought they might have gone, but they were just no where to be found.  We know they were sent, because they were also sent to my work gmail account, and they showed up just fine.  I assume this is some kind of Comcast filtering going on that is blocking certain emails before they even get to our account.  This is annoying, as it has been blocking emails from my child's school, and from businesses that we have signed up for newsletters or email notifications.  What can I do about this so that all emails get through, regardless of what they are or where they originated?  I would like to determine what is and what is not spam, not have Comcast automatically remove email they feel like blocking without me even having a clue that it was there.

Now to add to this, we noticed the opposite problem happening last night.  My wife received an email in our Comcast account regarding an online summer camp my child was doing.  My wife forwarded the email from Comcast to my child's gmail account.  Comcast showed the email as sent, but it never showed up in the gmail account.  We also tried forwarding the email from our Comcast account to two other gmail accounts, and despite Comcast email saying it was sent, it never arrived at the gmail accounts.  We forwarded other emails from Comcast to those three gmail accounts, and they were received just fine, but the one email about the summer camp just would not show up in the gmail accounts.  Again, we checked the gmail junk and spam folders also, it wasn't there either.  Since we have had issues receiving emails in our Comcast email, I am guessing that this issue with an outgoing email also has something to do with something Comcast is doing behind the scenes that is preventing the email from being properly forwarded on to the gmail accounts.  Are the issues receiving emails and this issue of a forwarded email disappearing and not reaching the recipient related?

The bottom line is, I don't want my emails being "pre-filtered" for me by Comcast, coming or going.  I want to receive what is sent to me, and I will decide if it is something that should be marked as Spam and filtered out, or if it is something that is legitimate I want to keep receiving.  I don't really want to stop using the Comcast email, as we have used it for years, but it will become a necessity if we aren't receiving emails any more from legitimate senders that we know we should be receiving from.  I'm looking for any guidance on how I can make some change(s) in settings that will stop Comcast from pre-filtering these emails, or something that someone at Comcast can do so that all my emails are getting through.

Thanks!