Mrs A deals with Wickes, by email, getting bits for her garden (she's not in the building trade).
Their email address is wickescustomerservice(at) wickes.co.uk.
Without exception, their emails to her (/at/ virginmedia.com) do not get through.
If she goes to Virgin, she can log in and see the emails there in the inbox, and transfer them to her Mac (on Virgin's inbox list, they are 'crossed out').
Why have Virgin taken against Wickes? Is it that the Wickes email is a 'co.uk' address?