1 Jun
2017
1 Jun
'17
3:33 p.m.
I think an adequate explanation for the URL-fetch mystery is that some people run a virus scanner or have their e-mail delivered to a mailservice that does scanning, and this scanner fetches all URLs in the message to check if they point to malware...
No amount of validation of the subscribers will solve that problem. The only thing you can do is obfuscate the links, but that is incovenient for the reader.
Similar problem: whenever you download a program, a second fetch is done by Microsoft/Google/Apple/whatever your favorite vendor to check what it is. I have seen this several times on a download server we run at work.
Rob