I noticed that when I print a letter using my desktop laser printer the letter looks great when I put it in the envelope and mail it. However, when the envelope arrives at the address I mailed it to, quite often the letter has toner offset on the portion of the letter where the type rubbed off on the paper. I’ve noticed this on many of the letters that I’ve received in the mail as well.
In doing some research, I’ve learned that the U.S. Post Office uses high speed mail sorting equipment and this equipment puts sufficient pressure on the envelopes to make the toner offset. The USPS ran a lot of engineering tests years ago and concluded that though there are steps that can be taken to mitigate the effect, it cannot be entirely eliminated. This happens with letters produced on the desktop as well as those produced by high-speed laser printers. So, a letter produced with toner, is prone to offset.
There are few solutions to this problem that are viable – fold the letter “outside” so that any toner transfer will be to the inside of the envelope; mail the letter without folding it in a booklet envelope, or add a slip sheet where appropriate to receive toner transfer.
The slip-sheet is a hassle and can look odd when received, the 9 x 12 envelope is more expensive to mail, and if you fold a letter “outside” then the content of the letter can be read through the envelope. The mailing industry has moved past this issue (it has been around for 8-10 years), not having come up with an easy solution to the problem. So I recommend folding a letter “outside” when privacy is not an issue or spend the extra change to mail the letter using a booklet envelope in a 9 x 12 folder and include some other useful material at the same time.
Any way you choose to go, the cost will be more expensive than sending an email with a pdf attachment however the impact of your personal letter should far outweigh the added expense and effort required.