Of course you may send multiple posts dealing with a given topic. Post regularly throughout the project period, rather than making all your posts on just one date. Part of the interest of the mail is to see how your thinking evolves as you complete the readings, hear the ideas of others, and begin planning your own website. Your posts should reflect this evolution. Do not wait until you have figured everything out before posting.
Email is somewhere between conversation and formal writing.
The more casual attitude towards grammar, syntax, and other properties of formal writing reflect the often improvised, spontaneous quality of email.