Comcast's email service really really sucks. Some legit emails about transferring a domain have taken over a week to arrive in my email box and when they finally did arrive they showed up in the spam folder which I had to practically jump through hoops to find.
As a test I've sent some emails to myself and they have yet to arrive and it's been about a week. Nothing about them being rejected either. It would be nice to know these things. because I host my brother's business website. They don't use me for email but if they did it could potentially be costing them business.
I also find sending email through them to be unreliable. half the time when I go to send email through my comcast account I cannot even log in.
Their new webmail is painfully slow and ugly. That's just my opinion though and I was never really a fan of webmail.
As much as I complain about their email I cannot complain at all about their high speed internet service. It's really pretty rare to have any issues with the connection and if I do it's usually resolved within a few minutes.