AT&T Yahoo Email Address Verification and Sendmail

In my last post, I described how to send mail from an Unix server with AT&T Yahoo! DSL line because SMTP ports are blocked and you have to send emails through Yahoo's secure SMTP server. Now AT&T added another restriction. I received the following email from AT&T:

Dear AT&T Internet Services Member,

We have received questions regarding the following error message which is received by customers when they send e-mail using a non-verified e-mail address:

“Unable to send the message. Please verify the e-mail address in your account properties. The server responded: 553 From: address not verified.”

Ah, it requires that the sender's address to be verified. The hostname of my FreeBSD server is not in public DNS server so it can't really receive emails so there is no way to verify the email address. Fortunately, Sendmail allows you to masquerade sender's address easily. You just need to add the following three lines into your sendmail.mc (Don't forget to apply the patch to the result sendmail.cf if you want to use sendmail with stunnel on localhost, as described in my last post)

FEATURE(masquerade_envelope)
FEATURE(genericstable, `hash -o /etc/mail/genericstable')
GENERICS_DOMAIN(your_domain_name)

Replace your_domain_name with the email domain that your Unix server uses. Then you need to modify /etc/mail/genericstable file. The syntax is pretty simple:

user1 verified_address

The verified_address doesn't have to be from yahoo.com. Any email address that you own and verified with Yahoo will do. The genericstable file basically says that for those users at the generic domains (defined by GENERICS_DOMAIN) the sender address should be replaced with the verified_address. Make a hash out of the new genericstable file,

makemap hash genericstable.db < genericstable

Now restart sendmail and you are all set.