No, it is definitely not us sending emails.
Likely to be email spoofing where the 'From' address is set to be the Plakias Board email address.
Not really a lot you can do about this with the way email works in general.
Once an email address is 'harvested' then it is available for scammers to use in this way. Email addresses are harvested in many ways, lists sold etc.
Its happened to my personal email address, you generally know because you will start to receive email delivery failure notifications, so called 'backscatter'. Scammers bulk send emails to thousands of recipients (also harvested, lists sold etc.) and the ones that can't get through can be returned to the 'sender' i.e me/you because that is what the 'from' address says.
Annoying yes, but as long as you don't open any links or attachments from unrecognized sources then you should be fine.