Often times I get inboxes from people who offer investments with the promise of lucrative returns. Indeed, we should not be easily tempted because it is almost certain that it is a scam method and we should just ignore messages like that, because if this is true, I think the owner of the system does not want to share his secrets with others
Most likely, scammers get your mailbox from the bounty tables of projects where you participate. I have a separate mailbox for bounty projects and other projects, where it is likely that it will be published in the public domain. This helps me protect myself from spam and offers from various scammers.
I ignored them when I never remembered that I attended any of their mailbox specially when it comes to investing just to get their airdrops worth of 1000 dollars. Those who inbox us that seem to be stranger should not be entertained unless you will be compromised when you open the link that they gave to you. Some of the messages can be a malware or phishing site and it might direct you to unknown resources. It might cause your accounts compromised and easily open access to hackers.