Dear Cory,
Thanks for the reply. Yes, this happens now only after updating to Sierra. I was perhaps reluctant to update on my mid 2010 MBPro, but kept getting nagged and thought it might be fun, in spite of a total lack of interest in Siri and most other 'advances' advertised. It has slowed me up quite a bit. Probably a mistake, but... Still running El Capitan on my iMac. Detest having always to update apps overmuch. Would be nice to have an update amnesty some time, but there is always the competition looking over Apple's shoulder of course.Yes, the pref you mention is checked. The emails in question are those from companies with a lot of gifs of products and offers, and instead of the pictures there are just lines of highlighted urls. which seem not to refer on to Safari when I click on them. Sorry if I was not sufficiently clear and precise in my original question! So far the only 'bug' apart from slowing up generally.