[exim] Rejecting direcly connected customers at connect time

I'm thinking of rejecting connections from some 'spam problem areas' in
the connect acl.
Below are the config I wish to use.
Does anyone have anything to comment? Might I end up with some
unexpected problems? Are the regexes matching the end users and do their
ISP's really serve them with mail gateways?

Regards,
Andreas

# comcast.net
deny  condition = ${if match 
{$sender_host_name}{\N^c-.*\.comcast\.net$\N} {yes}{no} }
      message   = Use your ISP's mail server to send mail

# rr.com
deny  condition = ${if match 
{$sender_host_name}{\N^cpe-.*\.res\.rr\.com$\N} {yes}{no} }
      message   = Use your ISP's mail server to send mail

# verizon.net
deny  condition = ${if match 
{$sender_host_name}{\N^pool-.*\.verizon\.net$\N} {yes}{no} }
      message   = Use your ISP's mail server to send mail

# wanadoo.fr
deny  condition = ${if match 
{$sender_host_name}{\N\.abo\.wanadoo\.fr$\N} {yes}{no} }
      message   = Use your ISP's mail server to send mail

# proxad.net
deny  condition = ${if match 
{$sender_host_name}{\N\.(adsl|fbx)\.proxad\.net$\N} {yes}{no} }
      message   = Use your ISP's mail server to send mail