[exim] Why the dodgy HELOs?

On Thursday 06 October 2005 16:39, Tony Finch wrote:

> There's a kind of spam software which sends messages with multiple
> recipients, and which says HELO using the local part of the first email
> address. My configuration uses an ACL variable to remember this so that
> subsequent recipients are also rejected. e.g.

I still don't understand the spammers' motivation for this -- it doesn't
seem difficult to reject obviously dodgy HELOs. What do they intend to
gain by reporting an invalid HELO for the client (since the server knows
the client's IP anyway)?