Ricoh Aficio SP 5210DN Hardware Manual page 143

If the curl is severe, flatten out the envelopes using your fingers, as shown in the illustration below.
If envelopes are severely curled after printing, flatten them by bending them back against the curl.
9. Load envelopes into the paper tray, with the print side down and the flap on the left as
shown in the illustration.
CBK240
CBK241
CEC262
Loading Envelopes
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