Why is my BIS Email on my Bell Mobility 9900 so slow?

I've searched the forum and see similar complaints about delayed emails from many years back and various providers. For some time now, my 9900 has been very slow to receive emails from my Rogers/Yahoo mail account. Gmail and BlackBerry mail are fine. I've resent Service Books and registered the Host Routing Table. Any idea why this is happening?

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Thanks for your reply, Bla1ze. I'm not experiencing any of the issues in the Knowledge Base Article. I do receive emails from Rogers/yahoo, but they are delayed. Sometimes only a few minutes. Other times up to 8 hours. Webmail is fine. I even receive with no issues on my Playbook. The archives show this behaviour across all providers and I've never seen a solution. I wonder if Bell is not properly supporting/provisioning BIS. Any other Bell BBOS 7 users having issues??