John R Pierce wrote: > Christopher Chan wrote: >> >>> configure your sendmail to use your ISP's mail server as a 'smarthost'. >>> >> >> How is that going to help the dest mta verify his address? > > it won't have to. his ISP will accept mail from its own customer's > IP address, same as if they were end user mail clients, and it will > relay for him. the destination MTA will presumably accept mail from > his ISP's mail server, unless they are a known spammer. > The dest mta is most probably doing a blank sender address verify on all emails. Although running a mail server on a dynamic ip is discouraged and use of the ISP's relay box is encouraged, I doubt that in this case that it will make any difference unless the dest mta has the ISP's ip(s) whitelisted which I doubt every much. The solution is to use a verifiable returnpath with bonus points for setting DS.