Ideally, sift through the masthead of each literary magazine you're submitting your story to. Try to address your pitch to the appropriate editorial staff member by name. It'll show them you've done some homework.
Your pitch should be pretty concise, because as a literary person you probably know that they have a lot of submissions to read and review in addition to potentially having a full time job since most literary magazine staff are volunteers.
Keep in mind a few things that are must-haves:
-Where have they seen your work before and/or what are you credentials for writing the thing you're submitting?
-Why is the thing you're submitting a good fit for THEIR magazine? If it fits with stylistic choices made by past authors in their magazine or a specific theme they have for that submission season, that's even better.
To bookend your pitch, introduce yourself briefly. Conclude very simply and concisely by thanking them for their time and sign off on your email.
I would also recommend having a writing-specific email. Since creating an Outlook account or a Gmail account is free, it's good to do that and have it be something very simple as well. It'll look better than having shannonlovescorgibutts3785241@yahoo or something like that. I used my own name and interest in corgis there to not poke fun at anyone other than myself. That is also not a real email that I have just to clarify.