[exim] regexp filter not working

This should be simple. I want a filter that matches any address
beginning with "d." but nothing else. The regexp should be:

    d\..*@domain.com

but that matches both d.abc@??? and delta@???. It should
not match the latter. I've tried multiple backslashes, but still no
luck.

I'm using Exim 4.44.

Help, please!