Questions[aptitude](server)

I have postfix email server on Ubuntu 11.04 version. I upgraded installed packages using the following command

sudo aptitude update && sudo aptitude safe-upgrade

Once I update those packages, I couldn't connect my email from my client machine. So I tested my postfix server using telnet.

telnet mail.mydomain.com 25

I got the following result for the above command.

Trying 127.0.0.1...
Connected to mail.mydomain.com.
Escape character is '^]'.

I am very new to this postfix server. I couldn't understand whether my postfix server corrupted or not? Why I couldn't connect my email after updating the packages?

Sometimes when installing a package, aptitude recommends several other packages.

Is there a way to show all previous recommended packages of all installed packages?

Edit:

Thanks for the replys so far. I already tried:

aptitude show ~i | grep '^Recommends' | cut -d ' ' -f 2-

Thats mostly ok. But it gives also things back like:

 console-setup | console-data (>= 2002.12.04dbs-1)

I want an easy way, to install all missing recommended packages.

So

 aptitude install console-setup | console-data (>= 2002.12.04dbs-1)

won't work ;-)

Is there a way, without manual checking all entries, to do this?

Frequently I know the name of the command line program that I need but I don't know the name of the package that provides the program. How do I find the name of the package that contains the program that I need? On RPM based systems they have the whatprovides option rpm -q --whatprovides /usr/X11R6/bin/xclock which will find the correct package. Is there anything similar for Debian based systems?

Say you're running a server and you don't want to upgrade to Testing (Squeeze) from Stable (Lenny) to just install a required package or two.

What's the best way of installing only certain packages from Testing?

I need to find the last time that the

apt-get update

command was run on my server. How can I determine this information?