Question Author
Hi, thanks to everyone who made helpful suggestions. We do already have tight parental controls on the computer, and as I'm the only person in the house who knows the password to override them, then I'm fairly confident that no-one has been accessing dodgy websites. Plus my kids are at the age where they are far more interested in downloading the latest lego game than in looking at anything that might remotely have to do with sex. Or so I've thought.... We do have Outlook set to block any pictures anyway - for example, when I get emails from John Lewis and M&S alerting me to sales, all the pictures are blocked. But this new spam has the pictures in the email without them being inserts or attachments, if that makes sense, so they don't get blocked. I don't open these emails and delete them straight away, but bits of them are shown in the preview pane. I'll take your advice about switching the preview pane on and off. I guess Spammerrs always have ways of getting round things though. My son (aged 11) is asking for his own email address, but I will be saying no if he is at risk of getting this sort of stuff.
Thanks for your help,
Growbag