Postfix and Sendmail - newbie question
Hello, I've just installed Postfix in my box...And I try to start it, it report OK, but it didn't start at all...
Then I notice in the description of Postfix and Sendmail, they are both MTA... So I think that maybe there's only one MTA can be run at a time... I shutdown Sendmail and start Postfix, everything gone well...
I do some search and saw that Postfix is better than Sendmail, so I want to use Postfix

But I don't know if I stop using Sendmail, switch to Postfix, is there any problem?
For example, PHP's mail() function use sendmail to send mail (or course)... is there any relation between /usr/sbin/sendmail and Sendmail?
And the last, can I run them simulately?