I’ll post it right away post = write to publish ( post a comment , or post a note ) right away = immediately , right now or post something via mail box ( send a letter )

If it is a letter "to post" can mean "to mail." That's British English. American English just uses "to mail" or "to send." "To post" also means to put something like a message or a comment on the internet, usually in a forum. That's an American English use also.