Does "Mark as Spam" Actually do anything?

[#1]

Yesterday and today I've received about 20 emails with the subject line "Test Message <number> with the body of the email a paragraph or two of random text. There are no links or images or attachments to try tempt me to open up or click through to a malicious payload/website. I've marked all of these emails as Spam, but does this actually do anything, other than move them into my Junk folder? If there is a Spam filter on the PN email servers I would have expected this to have picked up these emails and dealt with them?

[#2]

I don't know how Plusnet spam filters work; or indeed in any detail how any others work.  They are likely to take some time to build up knowledge.  Also it seems they have particular difficulty with short messages with no links; with so little information to go on it would be very easy to generate false positives (eg mark good messages as spam).
I used to use Yahoo as my main mail and moved to Google several years ago, mainly because their spam filters were better at that time.  They have remained very good, but I still get quite a few short messages that are obviously spam to me but that the gmail filters don't catch.

[#3]

Marking emails as Spam certainly in time weeds them out. For some reason I'm getting lots of betting emails at present and virtually all are trapped. My main concern is things being wrongly trapped - it would be nice to have a much simpler whitelisting action whereby you could just hit a "whitelisting" button on the Spam screen instead of having to delve into settings and copy each email address across.