As a publisher, let me give you a word of warning.
No matter how excited you are - take time to read the submission guidelines carefully.
If a publisher states to only include the first x-amount of chapters - include that exact amount. Do not include more, do not include less.
If a publisher states not to include attachments - do not include attachments! If you include an attachment when the publisher's guidelines request the information be pasted into the body of an email, it is extremely likely that your submission email will be deleted - no matter how good your chapters may be.
If they request a bio, work history, and a little bit about the book - make sure to include that information. If they ask for your social media links or a light marketing plan - don't forget to add that in. Read and reread the guidelines... then read and reread your submission!
I understand that publishers become a blur when you're sending out submission after submission... but the same happens on our end. We see a high volume of submission emails come through. There is always another one behind yours. And keep in mind, if we think you can't follow simple directions now - what's to say you'll be easy to work with later? Publishing is a non-stop, busy industry... especially for the smaller presses that wear a lot of hats. If you want to make sure your submission has a fair shot - follow the directions!