ClamAV 0.95.3 212.40.106.nnn morci.graphart.hu ----- I hate when this thing comes calling. Darn thing took close to 2,800 files from one of my main money sites before I finally realized what was going on and stopped it.
Clamscan's command line includes a switch "mail-follow-urls" to "Download and scan URLs". I suspect that's it. As far as I know it's not enabled by default, although it may augment scans for phishing URLs.
It would need someone a bit clued up to set this as clam is poor on user interfaces.
Because of my browser project I need to see how UAs behave so I usually let everything in and then only ban if the behavior is excessively egregious, like the Bing bots. It's because one of the things I do is recommend which UAs are ban-worthy. This version of Clam is now banned. But if a new one comes calling it'll be able to crawl until it does something bad enough to warrant my intervention.