email showing sent but never received

you have an email client accessing port 465 that is failing authentication(wrong password). Once you resolve that - email should be back to normal. 

@ComcastCSAEmail , thank you, but I'm using Xfinity Connect, not an email client. Is there something else I'm missing? It appears to be random as well, such as some will go through and some will not to the same email address.

check any built-in apps with a mobile device or tablet on the Verizon network. Most of the mentioned devices have a mail app built it. Its possible one of them may have been set up with your email and after a password change were not updated and causing issues. 

I'm having the same problem.  The emails appear in my sent folder but no one receives them.  I narrowed the problem down to a slash symbol "/" in the body of my first email.  When I removed the slash symbol and sent the email again, the people I was sending the email to all received it.  Now it has happened again with a second email.  This time the problematic symbol is a "$" dollar sign.   It is definitely a problem on the Xfinity end of things as I am sending these emails to people with various email providers (including Xfinity) and none of them are receiving my emails.  My programmer sister said that some programmer at Xfinity probably mistakenly introduced this "special character" problem when making a software change and now we have to wait for them to discover and fix it.   I'm adding my voice here so that maybe it will be discovered sooner rather than later.

@XX881 Can confirm not an issue in programming, but rather one with the spam filter. Your emails were getting flagged as spam/phishing and consequently getting blocked. This issue should clear up for you in the next 5 minutes. 

I am having the same problem. My emails say sent but the recipients aren’t getting them. How do I fix this?