Many years ago, a tribe of cannibals abducted me, strapped me to a chair, put me in front of a FreeBSD machine, and forced me to go without food, water, or pie until I had configured a working Sendmail server with SMTP authentication, TLS, and anti-spam features. After several days of intense, searing pain, I achieved victory, and the cannibals sent me on my way, scarred for life.
Ever since then, every mail server I've set up has used Sendmail. People told me Postfix and Qmail were easier to use, but I laughed at them. I had conquered Sendmail. I knew how to make it do my bidding. It had been a long, hard battle, but Sendmail was my bitch. Why would I want to start all over with something else?
And yet, every time I set up a Sendmail server, something inside me twitched, as if Satan himself had just bitten off a tiny piece of my soul. In spite of my hard-won Sendmail expertise, I knew, deep down inside, that there were better tools out there. Tools that I could use, if I would only commit to learning them. But then I remembered the pain involved in learning Sendmail. I didn't want to go through that again.
Nevertheless, the time came when I realized that Sendmail just wasn't capable of meeting my growing needs. Good MySQL integration, flexible virtual domains, the ability to reload config files without restarting the server, sensible config file syntax...Sendmail had none of these things.
I decided it was time to learn Postfix.
Today, I went from knowing nothing about Postfix to having a complete, working Postfix server with all the bells and whistles, doing everything Sendmail had ever done for me and quite a bit more, in about two hours. And it didn't hurt at all.