I don't know what email provider you use. Just 'sending an email to the spam folder' may not tell the server anything, only clicking the 'mark this as spam' or whatever equivalent command is. But...

Well, you have been told that already - but if they have been deleted, who cares what they are marked as? The point of marking something as spam is to help the email server learn what spam looks...

Gmail spam: I have only just noticed that, apparently, anything still in the spam folder after 30 days gets binned automatically - so no action should be needed at all. Has this not been occurring?

When you delete spam it goes into the bin. That does not mark it as 'not spam'. Emptying the bin removes it completely (after a while). Nothing here is mandatory, but every aspect you omit to...

This has to be one of the most difficult statements to parse that I have come across. Do you mean that no email apps have a 'more' option, only gmail's web interface?

What do you mean by 'maintaining'? What is there to maintain? If you mean the folder the spam emails go in to, just delete them. If you mean a list of spammer email addresses, it shouldn't require...