Hi,
You can try this, Frank: open Word, go to File > Print > Printer Properties (next to your Epson WF-3540 name), then under the Paper/Quality or Main tab, look for Paper Source or Tray Selection and choose Tray 2 for your letter paper. If Word doesn’t save that as the default, go to Control Panel > Devices and Printers > right-click your Epson printer > Printing Preferences, set Tray 2 as the default there, and click Apply. This tells Windows (and Word) to always print from that tray unless you override it for a specific job. Just curious, do you use both trays often, or is Tray 1 only for envelopes permanently?
Kind regards,