There is nothing more frustrating than your email getting overrun and filled with spam.
You really should avoid "forward" emails for starters. It only takes ONE person on any one person's email list to leak your email address into the wrong hands. When you send forwarded emails, have you ever noticed how many email addresses are included on them? If you get 10 people that send it to everyone in their address book and they have 15 contacts, that is 150 addresses leaked out right there. I have received forwards that easily have over 500 email addresses in them. If ONE person that receives that email wants to, they can distribute
your email address and everyone else listed in that email to anyone they choose.
I started a brand new fresh email account because of spam and ask that I not get forwarded emails. Then when I realized nobody would listen about sending them, I asked that they send me a "clean" copy. I asked if they must forward it, to please only send it to me separate from everyone else so that I could keep my email address private. I kept getting the unclean version so I dumped the account. Now I only have email for business and not for pleasure. The spam is that irritating to me. It was both family and friends that would not adhere to my wishes and kept sending "dirty emails" By dirty, I mean emails that included several other email addresses (along with mine) and was sent out to the masses with no regard for privacy.
Keep your email private and if you continue to get forwarded emails, you can put them on your blocked list but it won't stop them from still including YOUR email address to one that will end up in the hands of potentially hundreds of people if not thousands if it is circulated heavily enough. Your email is private. It is YOURS it is not for someone to breech your privacy and leak it to others. When a business does this, it is uncalled for. It is HIGHLY unprofessional to send out an email that shows everyone's email address. I do not do business with people like that. It's wrong! If they are in business, they should BCC clients and put themselves on the "to" line.
Start a brand new account and don't give it to anyone that doesn't respect your right to privacy. You can always tell people they have to send you private messages on forums or social media instead of email. They can't forward emails to your message box here.
I just checked my email that I dumped last year. There were over 3000 emails in it and 99% were spam. There was one from someone I know. I decided to see what it was. It was a forwarded email with over 135 (I lost count) email addresses on it. A lot of the emails had first and last names listed along with the email address. (in case you were wondering when someone sends you spam and calls you by your first name when your name isn't in the email address itself.) A lot of them even had actual links to click on to email any of the people that I wanted to myself. That should save spammers a lot of time.
My best advice to avoid it is to not allow anyone to have your email address that refuses to respect your right to privacy. Your email address is yours and should not be abused by people you know and allowed to get into the hands of thousands of people that you don't know and spammers. It is a snowball effect. I finally have a clean one and refuse to give it out. I have had to get rid of too many and start over because nobody would listen about not forwarding emails to me. If someone sent one forwarded email to me or one with several email addresses on it, they were marked as spam. It may sound harsh but if you knew how many people refused to listen about something so simple, you would understand the frustration.