Tip: When you want to reach out to retailers to submit your line, make an effort to find their preferred method of contact. When in doubt, I suggest email, with a follow up snail mail.
Why: If you don't, you risk them ignoring or being annoyed because it shows that you don't value our time or process. Often retailers have created a system
How: Check their website first, often they will tell you exactly how they prefer to be contacted. This is especially important if they have a separate submissions email or address - if they have taken the time to create a system for submissions, you want to follow it. If you can't find any, this is the one time I would say it's ok to call, simply ask how they prefer to receive submissions and whose attention you should put your submission to.
Want to tailor this advice to your line? I'd love to help! See more about my consulting services here. Looking for some tips now? Read my Brick + Mortar column on Oh So Beautiful Paper.