hi gmail ignores dots / no dots and capitals / no capitals in email addresses, so its a very common error of someone giving out your email address by mistake and thinking it is theirs
you can reply to the sender to inform them or filter them to trash
you own all variations of youra...@gmail.com and there
are no other Gmail accounts that have your account name with / without
the dots or capitals / lowercase in them , and no one else has access to your mail
you can email yourself on all of these to test as well as logging in using any of these variationsand YOUR password , also go to mail settings > accounts > send mail as > add address you own > type that account name with / without
the dots - you will be able to add it without a confirmation mail being sent because you own it
also to prove this log out , click create account , type 5 letters and a dot - it will say " Please use between 6 and 30 characters."