[header] How to mail a letter [title] Choose an envelope. [step] It's important to find the right envelope for your letter. If you choose an envelope of very light construction, for example, any heavy contents might break through the envelope while it's in transit. 
Take the following factors into consideration as you choose an envelope : [substeps] The weight of the paper. The weight of the envelope should be appropriate for the weight of the paper and any other contents you may be mailing.