Spam In Email Link Query

This may not be to do with eM Client, but i’d be very grateful for any pointers.

I got an email from my local borough council with a link to one of its webpages. I used it and it worked fine. A week later i wanted to visit the linked page again, but i had deleted the original email. I found my reply to the original email in ‘sent’ and followed the link again, but this time it took me to a log-in page for When i found the original email (rather than my reply to it) the link worked was fine.

I’ve never heard of and i wondered how the link could have been corrupted in this way. I’m scanning the PC as i type but it doesn’t seem to be picking up any infection and i have regular scans withWin10 antivirus and malwarebytes. has anyone any idea what’s going on please?