I just received an email from a registrar saying that a domain name I
had registered with them was due for renewal in September. This was
not correct, the domain name in question was not registered with this
registrar. The renewal URL given in their email takes you to a Domain
Name Renewal/Transfer form which states that if your domain name is
not registered through xxxxx  ........ your domain name will be
transferred.

This seems an unethical way to do business. I am sure that some people
will not remember who their domain is registered with and will assume
that the email is from their current registar. They will then fill out
the Renewal/Transfer form to renew the domain and thus unknowingly
transfer it away from their current registrar.

-- 
Best wishes,
Malcolm