If your Brother MFC-L6700DW is jamming, smudging, or misfeeding when printing envelopes, you're dealing with one of the most common printer repair requests for this business monochrome laser all-in-one. The MFC-L6700DW handles standard paper reliably, but envelope printing issues typically stem from incorrect tray configuration, improper envelope loading, or fuser temperature mismatches. This troubleshooting guide walks you through proven fixes that resolve envelope printing problems without unnecessary service calls.
Common Causes of Envelope Printing Problems
Before diving into fixes, understanding why your Brother MFC-L6700DW envelope printing issues occur helps prevent recurrence. This 48 ppm laser printer uses a 300-sheet standard tray and 50-sheet multipurpose tray, but envelopes require specific handling. Thick stock, moisture content, adhesive strips, and incorrect print driver settings all trigger feeding failures, wrinkled output, or toner that flakes off envelopes rather than fusing properly.
Step-by-Step Troubleshooting for Envelope Printing
1
Use the Correct Envelope Specifications: The Brother MFC-L6700DW officially supports envelopes measuring 3.5" x 5.8" to 6.5" x 10.2" (Com-10, Monarch, DL, C5). Avoid glossy, embossed, or window envelopes with the window on the feeding side—these cause jams. Use envelopes with the flap on the short edge, and ensure adhesive strips are fully sealed with no exposed glue that could melt in the fuser. Store envelopes flat in a low-humidity environment before printing to prevent curling that triggers multipick errors.
2
Configure the Multipurpose Tray Properly: Open the MP tray fully and extend the support flap. Load envelopes with the printing surface face up and the short edge feeding first. Slide the paper guides snugly against both sides of the stack—loose guides cause skewed feeding and creased corners. Set the paper guides to the exact envelope width; the MFC-L6700DW's sensors detect guide position for proper registration. Never load more than 10 envelopes at once in the MP tray to reduce pressure on the pickup roller.
3
Adjust Print Driver Settings for Envelope Media: Access Printer Properties in your application or Control Panel. Under the Basic tab, change Paper Source to "MP Tray." Click the drop-down next to Media Type and select "Envelopes" or "Thick Envelopes" depending on your stock weight—this slows print speed and increases fuser temperature for proper toner adhesion. In Advanced settings, verify Paper Size matches your envelope dimensions exactly. Mismatched settings cause the printer to default to standard letter timing, resulting in misaligned text or fuser errors.
4
Clean the Pickup Roller and Separation Pad: Envelope debris and paper dust accumulate on the MP tray pickup roller, causing intermittent feeding failures. Power off and unplug the printer. Open the front cover and remove the toner cartridge and drum unit for access. Locate the MP tray pickup roller above the tray opening—clean it with a lint-free cloth dampened with isopropyl alcohol. Check the separation pad for wear; a glazed or flattened pad allows double-feeding. For persistent Brother MFC-L6700DW envelope printing issues, replace the pickup roller assembly (part number LU9215001) if cleaning doesn't restore consistent single-sheet feeding.
5
Check and Adjust Fuser Temperature Settings: Toner flaking or poor adhesion on envelopes indicates insufficient fuser heat. In the printer's onboard menu, navigate to Machine Settings > Print Settings > Envelope Enhance Mode and set to "On"—this extends fuser dwell time for thicker stock. For Windows users, access the BR-Script or PCL driver, go to Device Settings, and enable "Thick Paper Mode" for envelope jobs. Avoid running envelope batches back-to-back without cool-down periods; the fuser unit in the MFC-L6700DW can overheat and trigger error code E50 or cause thermal shutdown.
6
Update Firmware and Test with Alternative Envelopes: Outdated firmware causes communication errors between driver and printer that manifest as envelope misfeeds. Visit Brother's support site, download the latest firmware for MFC-L6700DW (check current version via Machine Info > Version), and install via USB or network connection. After updating, test with a fresh ream of #10 envelopes from a different manufacturer. Some recycled-content envelopes have inconsistent fiber density that confuses the printer's media sensors. If standard 24 lb. wove envelopes feed correctly but your preferred stock fails, that specific envelope construction exceeds this printer's specifications.
⚠️ Important: Never forcefully pull jammed envelopes from the fuser area—this damages the fuser film and pressure roller, requiring costly replacement. Always open the rear cover and follow the jam clearance path indicated by the green levers. If an envelope has partially entered the fuser and torn, power off the printer completely and allow 10 minutes for the fuser to cool before attempting removal. Exposed fuser components reach 400°F during operation and cause serious burns.
Frequently Asked Questions
Why does my Brother MFC-L6700DW crease every envelope I print?
Creased envelopes almost always indicate incorrect loading orientation or paper guide misalignment. Ensure you're feeding short-edge first with flaps closed and sealed. Verify the MP tray guides aren't overtightened, which pinches the envelope during transport. Also check for obstructions in the paper path—remove the drum unit and visually inspect for torn label fragments or toner buildup on the registration rollers.
Can I print envelopes from the standard 250-sheet tray instead of the MP tray?
No—Brother explicitly requires envelope printing through the multipurpose tray only. The standard tray's curved paper path and pressure rollers aren't designed for envelope thickness, virtually guaranteeing jams and potential fuser damage. The MP tray provides a straighter path with reduced curvature that accommodates rigid stock. Attempting envelope printing from Tray 1 voids warranty coverage for resulting damage.
How do I fix smeared or easily rubbed-off toner on envelopes?
Smeared toner points to fuser temperature too low for your envelope stock. First confirm you've selected "Envelopes" or "Thick Envelopes" in both the application and printer driver—setting mismatch is the most common cause. Enable Envelope Enhance Mode in the printer menu. If problems persist, your envelopes may exceed the printer's 163 gsm maximum weight rating. Switch to lighter 20-24 lb. envelope stock, or consider using a printer support service to evaluate fuser wear if standard envelopes also show poor adhesion.
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