MFC-8840DN FAQs & Troubleshooting MFC-8840DN Not your product? Sort by: Updated Date Popularity 2 Results 1. 24/08/2006 How do I improve the copy or fax quality? 2. 24/08/2006 Why are my sent faxes always received with a black vertical line down the page? Fax FAQs & Troubleshooting