It's unlikely that you've deleted Outlook Express, simply the link to it, bagpiperay.
However, if you want an email client that a lot of people find superior, more configurable (through extensions and themes, and also in its basic configuration if you're up to that) and more secure than Outlook Express, you could try
Mozilla Thunderbird. It's free and open-source.
You could also try the companion browser,
Firefox, which is simarly favoured by many people. Myself among them , of course! ;-)