Suggestion: UNSUBSCRIBE & Check Address
You read the email header and detect a "unsub" tag in the header - just do NOT consider all "unsub" to be spam, it is the other way around.
Then very often the reply-to, from and unsub is to an invalid email / URL so can you insert the option "Check address" and "Check URL". Check address with "HELO <address>" or finger(). All status of category not 0 == OK should be shown. The usual will be "550" - "User not known". For URL - make a"ping" or "Lookup", again any non-zero return sugggest an error. No need to check certificates, that is my problem, 99.99% of links that fail are improper URL. But here, status 550 suggest a fake certificate should you "stat" the URL.
The same may be made available in all "Compose" to enable verification of rarely used email addresses. People move on.
Knut H Flottorp
shared this idea