Email confidentiality footers annoy me. I see them frequently on many emails that I get and I think of them as meaningless text that really should be ignored. That an email is somehow a private exchange of information is laughable. Email is sent in plaintext using an open protocol and on the wire it’s all unencrypted.
What really brings this to the forefront is when I see these meaningless bits of mental flotsam and jetsam clogging up my email box because someone set a vacation autoresponse and their membership on a email list is causing them to constantly reply with a “I’ll be out from…” email with this stupid block of text at the bottom asserting that the email is the property of blah blah blah.
Writing email has the same security protections as writing a postcard and tying it to a bird and letting it fly off. Your assertion that your communications are somehow proprietary or classified is utterly hilarious.
If people really wanted to make this not so utterly irrelevant, they should use public-key encryption or at least something like ROT–13 encryption so that the text isn’t readily apparent and takes some work to decode. Sending plaintext with this silly block at the bottom just musses up the display and doesn’t mean anything to anybody. So stop it.