Comcast not working with 3rd party email clients from one specific ISP.

Hello,

I seem to have a weird problem where my Outlook client (or any other third party email client) cannot download any new email from my Comcast account, when I am connected to a specific 3rd party ISP. The problem occurs only when I am connected to Videotron in Montreal. I have tried this with multiple Videotron locations. Works fine with Bell. Works fine with any other ISP I have used in my travels. The same problems occurs with Apple Mail, Google Gmail or any other email client I have tried. Regardless of whether I am using iOS, MacOS, Windows. Any of these clients work fine if I use a mobile connection on my cell phone. The moment I connect through a Videotron ISP,  Comcast email stops downloading. I have had a few discussions with Comcast support on this trying to get it resolved. It's frustrating because by the time they call back a few days later, I am no longer in Montreal and cannot test anything. The problem seems to be only with  Videotron and only with their email server. As if they are blocking IP addresses specific to Videotron. 

The biggest surprise today is that the Xfinity level 2 rep told me that as long as I can access my email using the browser based interface then it's not their problem. They don't guarantee support or that their email works with 3rd party clients. When I pressed the issue that there is no mention of this anywhere, I was told that I needed to do is log out from all my accounts and not use email for 48 hours. First she said that they found a problem with the IP address I gave them. When I asked what they would do during those 48 hours? She said nothing!! I should do that to see if the problem was resolved. If not, then I should contact Outlook support. 

I feel they are making up a story on the spot. Anyone else run into this issue? Any suggestions on next steps?