Use the "passwords" feature to check if one of yours is compromised. If it shows up, never ever reuse those credentials. They'll be baked into thousands of botnets etc. and be forevermore part of automated break-in attempts until one randomly succeeds.
Possibly related question. Layely I've been getting email 'replies' from various businesses and services (all over the country, USA) all about an 'inquiry' that I never made. Apparently someone just got my email address and is using that for -- what ? A couple questions:
** What is that someone up to, why doing that?
** Should I do something about that?
** What could I do? Don't want to change email address.
That's just your email address being sold by information brokers. Not illegal, not a reason to change your email address. Block, delete & move on.
Probably unrelated, domain spoofing is common, but miss-configured mail servers will accept those emails and process auto replies. They can also abuse input forms to try and send out emails, but that typically does not have much control over content.
If you are getting more emails than you can deal with, than can be used to try and mask other emails by burying them in a large email volume. In that case you should be looking for emails from important accounts you do own (eg banking.)