help finding friend in czech rep/germany

Lisa said he was driving to Berlin, and I'm not sure she even knows if he even made it to Berlin.
Only an idea, I know nothing, but since you know his email address, can you contact his server and explain this to them, and maybe they can trace any emails he could have made to his family or someone, and the dates he wrote them around the four days you didn't hear from him. That way you could know he was around on the dates after the last email he sent you. But it could be they wont give information to anyone outside of family. My idea may be crazy, but wanted to think of something! Maybe if it were myself, I would try anything, if it sounds crazy or not! However, if you decide to try this, I feel it would be a good idea to wait to try to find him because four days is not all that long. His family could be worried too, and they could try to find him also. Do you know if he has family,and do you know them if he does?
On a positive note,maybe his laptop crashed, and can't get to another computer! I've been to Berlin, and there is so much to see and do. Maybe he just doesn't have the time to get to a place where he can email. He may have no idea you could be so worried.
THINK POSITIVE!! Could be he's fine!

Try contacting his family. The U-S Embassy in Berlin would be made aware of any mishaps involving an American citizen, but it's unlikely they'd release info to anyone except a close relative.

This is crazy talk. Relax.

You haven't heard from your friend for 4 days. FOUR DAYS. That's not very long -- people go for weeks and months without sending email (may be hard to imagine, but it's true...actually I recommend trying it sometime).

Did your friend indicate that he would definitely be contacting you again within a specific period of time? If so, and it's been MORE than that ammount of time, then call his family, but by all means, there's no need to panic just because a few days have gone by and you haven't heard from someone who's traveling in Europe. It's not exactly like he's wandering around Baghdad.

Odds are, he's simply having fun traveling, which might actually be a sign that he's enjoying the trip (spending all one's time emailing back home several times a day just might be a sign that things are not going well).

IF you have a valid reason to think something has gone wrong (e.g. he PROMISED he would definitely contact you on Monday, and Monday goes by with no word, and Tuesday and Wednesday go by, too) only then would I make a calm inquiry with his family.

Don't bother traying to contact the company that handles his email, they're not going to do anything.

Bottom line - there's no need to freak out. Give it a little time and you'll probably hear from him soon enough.

About contacting his server if he is really missing, I just watch "Nancy Grace" on CNN much too often, and I get ideas like that! But listen to David, he is so right!
I hope you will keep us posted about what's going on with him. In the mean time, try to relax.