Yesterday’s Thoughts

June 8, 2005


Yeah! We have mail coming from the domain.

My ISP, Earthlink, blocks port 25, making it impossible for me to send mail from the domain to anyone except Earthlink Or Mindspring customers.

I can receive e-mail because I use the MailHop service from DynDNS, but I cannot send mail. Using MailHop, DynDNS receives my mail, and then forwards it to me on a different port. I could pay DynDNS to do the same with my outbound mail, but it is an additional expense and there are limits, which are pretty small, less than 100 messages a day as I recall. I would not exceed that amount very often, but I didn’t care to risk it.

I knew that I could send mail using my domain and by configuring my client software. I had checked into this before. Earthlink documented the work around on this FAQ on port 25 blocking. It was just a matter of Earthlink’s normal authentication through an alternate host using user name and password, but I didn’t know how to do this through sendmail, as I didn’t have much experience with configuring and administering sendmail.

There was an reference on slashdot today about some guy how claims to receive, and more significantly manage, 1 million spam e-mails a day. His story looks pretty interesting, and the layout and the clarity of the site were big pluses.

Before I got too far in the article, though, I started following along at home and poking through the sendmail configuration files. I saw the SMART_HOST configuration parameter. This seemed to address my problems with sending mail, “Uncomment and edit … if your outgoing mail needs to be sent out through an external mail server,” so I went off on a tangent. (I don’t receive that much spam anyway, courtesy the filtering that my upstream providers do for me.)

I Googled and the first hit was this page at

It was a piece of cake from there. My Whitebox system had the latest versions of Cyrus SASL and sendmail. It was just a matter of creating a few configuration files, making some other changes in the sendmail config, building the authentication database and the and restarting smtpd . It just worked.

The sendmail documentation is first rate. There are examples of how to do everything, including debugging. Example:


sendmail -d0.1 -bv root | grep SASL

and make sure SASL appears in the output. Otherwise go back to compiling sendmail and make sure your site.config.m4 is really used.

This is brilliantly simple and direct.

One of the configuration files specifies the authentication server and the user name and password to use for authentication on that server. In my case this is the Earthlink server, user name and password. I created a special user for just this purpose. I don’t see anyway that it matters, but it seemed prudent to do, so I did.

The downside was that I received a deluge of test e-mails from myself, to my various external e-mail accounts, but since most of them had some permutation on “Test” as the subject, it was easy enough to clear up.

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