You may receive emails that class themselves as being Spam.
Your Internet provider will have software analysing incoming emails and trying to weed out anything dangerous and mark anything that looks like unsolicited email from someone not in your contact list or white list as “Spam”.
Usually you have a range of options with your email from “block message from anyone you don’t know” (very safe option) through to “let everything through” (unsafe option).
You may also get a more interesting message on a spam email that says something such as “This email has failed authentication tests set by Walmart”.
Walmart is one of many large companies that use an extra layer of security for emails whereby they set up information on a public server and when emails claiming to be from Walmart arrive at your Internet provider they can automatically authenticate this against Walmart’s instructions (e.g. only a set IP address at Walmart is allowed to send out emails).
If the message fails, then it may be rejected but more likely to be classed as Spam and allowed through for the recipient to determine what action to take.
This extra layer of security is very useful but requires more work and is typically only used by large companies, banks etc. This is usually based upon the DMARC standard which is used by Google, Facebook, Apple, Craigslist, Virgin Media, British Airways, Dropbox, Amazon and many more.
Read the post at https://fightback.ninja/test/dmarc-email-authentication/ for more information on DMARC.
If you have any experiences with scammers, spammers or time-wasters do let me know, by email.