11027/28 mumbai chennai mail mein bhi rms hai aur 11041/42 mumbai chennai express mein bhi rms hai. yah mail express aur train ka name se kuch nahi hota asli matlab sirf coaches aur engine hai aur speed. jis coaches ke trains ko jyada speed se loco chalayeja usko SF bolte hai aur avarage ya slow speed se chalayega usko mail exp bolte hai.