However, writing software without defects is not sufficient. In my experience, it is at least as difficult to write software that is safe - that is, software that behaves reasonably under adverse conditions.

Defect-free software does not exist.

I was going to visit IBM for six months as a visiting scientist. Now, six months is a lot of time, so I came with a whole list of projects that I might want to work on.

I don't expect an overnight change of all desktops to what the US Military used to call B3 level security. And even that would not stop users from shooting themselves into the foot.

However, writing software without defects is not sufficient. In my experience, it is at least as difficult to write software that is safe - that is, software that behaves reasonably under adverse conditions.

I want to avoid locking people into solutions that work only with Postfix. People should have a choice in what software they want to use with Postfix, be it anti-virus or otherwise.

Qmail out of the box works fine, so people will want to use it regardless of licensing restrictions, even when the software does not ship with their system software.

When I write software, I know that it will fail, either due to my own mistake, or due to some other cause.

The challenge with Postfix, or with any piece of software, is to update software without introducing problems.

Sure, but competition is good for the user.

As of today, the Postfix mail transport agent has almost 50,000 lines of code, comments not included.

Like all software, Qmail can survive only when it keeps up with changing requirements.

Most of the effort in the software business goes into the maintenance of code that already exists.

Coming back to the topic of computer security, the TCP Wrapper is an example of such a safety net. I wrote it when my systems were under attack by someone who appeared to walk through walls.

This will surprise some of your readers, but my primary interest is not with computer security. I am primarily interested in writing software that works as intended.

For many people my software is something that you install and forget. I like to keep it that way.

At the time the Sendmail program had a very poor reputation with respect to security, with four root vulnerabilities per year for two successive years.

One bug in an SMTP server can open up the whole machine for intrusion.

Windows favors multi-threading, which means that a service is implemented by one single process.

Writing software that's safe even in the presence of bugs makes the challenge even more interesting.

Postfix keeps running even if one Postfix process dies; Windows requires that someone restarts the service.

Lack of documentation is becoming a problem for acceptance.

The Postfix security model is based on keeping software simple and stupid.

In a previous life I wrote the software that controlled my physics experiments. That software had to deal with all kinds of possible failures in equipment. That is probably where I learned to rely on multiple safety nets inside and around my systems.

My reply is: the software has no known bugs, therefore it has not been updated.

Adding functionality is not just a matter of adding code.

You learn from a conglomeration of the incredible past - whatever experience gotten in any way whatsoever.

I've danced one time in my life. It was the most mortifying experience I ever had.

The experience of life consists of the experience which the spirit has of itself in matter and as matter, in mind and as mind, in emotion, as emotion, etc.

My best film composing experience was with Elia Kazan.

Education is a private matter between the person and the world of knowledge and experience, and has little to do with school or college.

A novel should be an experience and convey an emotional truth rather than arguments.

By experience we find out a short way by a long wandering.

The experience of democracy is like the experience of life itself-always changing, infinite in its variety, sometimes turbulent and all the more valuable for having been tested by adversity.

Learning teacheth more in one year than experience in twenty.

Well, the hardest thing to do, as we know from our own experience on 9/11 is protect everything all the time.

The most important training, though, is to experience life as a writer, questioning everything, inventing multiple explanations for everything. If you do that, all the other things will come; if you don't, there's no hope for you.

When I reached adulthood, even now, I could afford to belong to a country club. But I could never belong to a private club because of my experience as a child, because it would isolate me from the whole of humanity.

No one I know of has ever had this experience-where you had to sit and wait and wait for a DNA test to come back just so you can write the last page of the book.

If you live long enough, you'll experience everything.

Actually I'd had a certain amount of experience in Europe in the inter-war period, as a banker, and I was also a member of the Board of Directors of the International Chamber of Commerce.

In the case of my book, I don't think it's really the coming-out gay novel that everyone really needed, even though it was received as such. The boy is too creepy, he betrays his teacher, the only adult man with whom he's enjoyed a sexual experience, etc.

Well, I go to the theater today, and its curtain - there is no curtain in this play; the lights go down and go up - and we start. And I live this character for two hours. There are only two of us in the play. And It's a complete experience.

Our job as writers and thinkers in the time is how to bring about the occasions that let people have that first-person experience - or the metaphoric experience that allows them to see human continuity as opposed to total threat, total willingness to do violence.

Experience is never limited, and it is never complete; it is an immense sensibility, a kind of huge spider-web of the finest silken threads suspended in the chamber of consciousness, and catching every air-borne particle in its tissue.

In my fifty years of experience and memory, I have seen the most amazing increase in the standard of living of a people ever achieved anywhere in the world. This is why I am so sure that our system of free competition and industrial development is sound and must be preserved.

The greatest gift is the passion for reading. It is cheap, it consoles, it distracts, it excites, it gives you knowledge of the world and experience of a wide kind. It is a moral illumination.

It's been my experience that every time I think I know where it's at, it's usually somewhere else.

The experience of learning how to get straight to the core of a problem proved to be of immense value later when I had a long succession of responsibilities in large, complex government departments.