Luckily so do @rifeljm, @dgurnick and @morphix, the authors of envelopa.com.
I just used their fine (free!) service to print 24 envelopes for season greeting cards I helped craft, together with my son and wife.
Envelope printing goodness for the lazy at heart.
The service lets you import addresses with no sweat, using CSV or pasted from a spreadsheet. Select your addresses, pick an envelope size, or set your own and you’re good to go.
Give it a shot now, will you?