Editing Apple mail with a web address

I am using Apple Mail 6.2. On one of my Macs when I type a web address (not a hyperlink) in the body ot the message it is converted to a link. If I then try to edit the line before the link after typing the first word the cursor moves to the end ot the sentence containing the link. If I creat a link rather than typing a web address, this editing problem does not occurr.

On my other Macs with the same Apple Mail preference settings, typing a web addres does not convert the address to a link and the editing works perfectly. How can I stop Apple Mail from converting a web sddress to a link, or correct this editing problem?