[username135]

This happens with my Gmail account.

I know periods don't count, supposedly, but I still get emails for someone with the same name as mine. My email is first.last, theirs is firstlast. I wonder how much of my stuff they get erroneously?

[__ryan__]

You are correct that the period doesn’t count. Both email addresses belong to the same account. A possible explanation is that they have entered your email as a mistake.

[OJFord]

The full stop doesn't count. If you're successfully using 'first.last', then theirs is not 'firstlast', that is also yours, as you said yourself.

Theirs is probably 'firstlaast' or something - i.e. some typo unrelated to their decision not to separate by '.'.

[dharmab]

A more likely explanation: https://xkcd.com/1279/