Rules to shipping by lettermail?

[generatorgames]

I am new to selling and am unclear what the rules are to shipping by Canada Post Lettermail. In particular, for items like trading cards and game manuals, can these simply be mailed in a regular envelope with some rigid paper/thin cardstock to prevent damage? Is there anything else I should know that is vastly different from small parcel shipping? Thanks for any clarification.

[rcrawford34]

I sell Old Postcards and have sent about 15,000 plus through the mail.

My cards are sent in  Non Acetate Post Card Sleeves  (Could be plastic but not advisable to leave them in that material it can damage the item over time).  The Non Acertate sleeves are used to store postcards but also can prevent water damage if the mailing gets wet or damp.  I place them between double sided thicker Cardboard and they are sent in a Size 0 Bubble Envelope.   The Envelope is stamped Please Do Not Bend.

I can send approx 10 to 12 cards in one mailing.   The cost for this as a Oversized Envelope is $2.20 within Canada and approx $3.10 to the U.S 

 The only  damage I had occur was on 3 expensive cards  sent as one mailing. It was the stupidity of the Mail carrier with these.  He/She folded the envelope in half to put it in the mail box.  

weavers

[generatorgames]

Thank you for the answer! I'll be following your method, a lot of good tips on preventing damage.