Your email client is smart. It keeps track of everyone you send messages to — whether they’re in your contacts or not — so if you ever need to send another email, it can offer to add those addresses via auto-complete. It’s easy to forget complex email addresses, and, as an example, having Mail help you type CustomerSupport@BigCompany.com can save you time.
These previous recipients are stored forever, or until you clean them out. While you may have contacted Support@BigCompany.com several times, if you no longer need to, Apple Mail will still offer that address as an auto-complete suggestion even when you want to write to, say, Support@MomAndPopCompany.com.
Because of this, it’s a good idea to clean out your previous recipients from time to time. You may want to delete most of them, but you may also want to add some of them to your contacts. Here’s how to manage your previous recipients in Apple’s Mail.
Read the rest of the article on the Mac Security Blog.