I have escalated this to the forum admins for follow-up. You should see a response in this thread from an employee. I use Puritan's Pride myself and I have no issues getting their emails.
Hi Markjd, I can look into this for you. Could you Please send me a private message with your account information (your name, username and phone number).
@madcal1 wrote: ... a message appears telling me that "my email address may be invalid due to them being unable to reach me at my listed address". ...
Are the messages in your webmail Spam folder? If not, check your Spam settings. Make sure that "Enable spam filtering" and "Save a copy of emails marked as spam" are both selected (see https://www.xfinity.com/support/articles/spam-filters-and-email-blocking-new-experience).
... I've double-verified that the address they have on file is accurate and even added them to my address book ...
Adding the sender's address to your address book won't help -- Comcast doesn't refer to it when deciding whether a message is spam. They should, but they don't.
@madcal1 wrote: ... I've added a filter for the three Netflix addresses ....
Worth a try, but AIUI filters only run on mail delivered to the Inbox. Since Comcast delivers mail they consider spam to the Spam folder and not the Inbox, filters don't act on such mail.
If messages that shouldn't be treated as spam are being delivered to your Spam folder, their Security Assurance group might be able to help you. Give them a call at 1-888-565-4329 (from http://constantguard.comcast.net/help/report-abuse/). Note that this is NOT one of the general customer service numbers. The first-line reps there are sometimes not very helpful. If so, be persistent, and keep at them until you get a satisfactory answer.
Without their help, the only thing you can do to prevent messages from going to the Spam folder is to turn spam filtering off completely so that everything they deliver is placed in the Inbox.
Thanks BruceW, I didn't have the "Save copy of emails marked as spam" checked but that has been changed. I can't imagine I marked all three as spam but to err is human so one never knows. Additionally, based of your comment about the address book, I've added a filter for the three Netflix addresses I had mentioned in my previous post. Time will tell and I'll update this post when I find out more. -madcal1
FWIW, I get regular emails from Netflix with no issues. You need to call the number BruceW posted and have them look at your account.