How do firms I've never dealt with get my e-mail address?

[Old Sparky]

I quite often receive unsolicited e-mails from businesses of various kinds with whom I have no recollection of ever having dealt, and, given that all (reputable) companies  have 'we value your privacy and will not share your data' clauses, wonder how and from where these firms harvest data. I always delete these unwanted e-mails so it's not a problem.  Several times  I've marked them as 'spam', and Blacklisted the stated source e-mail addresses, but still they arrive.  Maybe there's no way to completely eliminate them, but, as I indicated 'How do these firms get my contact details?'

[ppppenguin]

It only takes one firm to sell/give your email address, or get hacked, and your address is out there in the wild. Or you correspond with somebody whose PC etc has been hacked and their address book harvested.

[Refugee]

We had it after switching internet providers.
The new company did an Equifax credit check and then Equifax got hacked.
It took two hours on the phone to sort out the fake transactions on the bank account.
The hack broke in the news a few weeks later.

[ppppenguin]

I have my own domains (borinsky.co.uk is the main one as you can see from my signature line) so I can use email addresses of the form ********@borinsky.co.uk. When I register with an organisation I use a unique email address, usually of the form thatorganisationname@borinsky.co.uk. If that company gets hacked (it has happened more than once) I know where the leak was and can put that address on my block list. If I still use the company I can then change the email address I use with them.

This helps, but is far from a full solution. Most of the rest of the spam gets caught by a spam filter in my email program (Thunderbird).

[Terry]

Or you correspond with somebody whose PC etc has been hacked and their address book harvested.

Worse still, a 'friend' decides to send some stupid joke to everybody in his/her address book and uses cc instead of bcc. So you now have the email addresses of lots of people you don't know - and they now have yours!

The more strangers that have your address, the greater the likelihood that one of them will be hacked.

Both I and my wife have fallen out with friends in the past who refuse (or are too stupid) to understand the importance of using blind copy.

An old friend of mine - a retired physicist, so you would expect a reasonable level of common sense - decided I might like to be part of his jokes list but didn't seem to be able to comprehend the need for using bcc.

Fortunately it was an email account I rarely used because it suddenly started being spammed at an amazing rate!

At first I just deleted them but, out of interest I started moving them into a junk file for a few weeks so it was easy to count them.

Then I forwarded one day's worth to my 'friend' - individually, of course, - with a note telling him that 'this is what happens if you don't bcc.'

I did the same thing the following day, then forwarded one more on the third with a note saying 'I have 207 more of these received over a three week period. How many more would you like to receive?'

The 'jokes' stopped - which was no great loss - but I heard nothing more from him. After a few weeks I deleted the email account.

[ppppenguin]

I was going to make the point about big cc'ed mailing lists but Terry has beaten me to it. Totally agree with everything said.

CC lists are useful for a small group who need to keep in touch a lot. I'm on a couple of those.