When you open a spam email it only confirms to the scammer they have a valid email address & the recipient has taken the time to open it. Yes, they know if you open their email or not.
There are a lot of IFs attached to that. If you click on any links or attachments in the email or have the "read receipt" enabled, yes, your email client will respond, if you open the email. However, if you are just looking at the email, do not click on links or attachments, and have the "read receipt" disabled, nothing is sent from your email client. The sender does not know you opened the email.
Some email clients have a "vacation" option that allows the email client to automatically respond to any email. That is very poor choice for anyone to use. You should always know your email client.
The email that I talked about previously, is further filtered and only appears in my "spam" folder. In that folder, everything in the email (links, images, attachments, etc.) is disabled, so there is nothing to click on. Just a benign indication of what was there. While there are other spam emails, the ones that I was responding to, no longer are being received. For the other spam, which is only one or two a day, I just select them and select "block".
I have four email accounts that I check several times a day. Only one of those accounts actually gets any spam. And, that account only gets it through an old redirected MSN account. That account was supposedly deleted over 10 years ago.