you can use encrypted mail, however that requires you to convince all people that you exchange mails with to use encrypted mail as well.
You could use a hosted email service in another country where the american authorities don't have easy access. Europe might be an option. However, as with hosting your own email server, that's only a partial solution: If you communicate with other people, your mail is not only stored in your inbox but also in their outbox. So they'd have to use a mail provider outside the US as well - see the first paragraph.
The best is probably a hybrid solution: Try to educate as many people to use encrypted mail as you can and use a mail server that's located outside the US. It doesn't provide 100% protection, but at least you're not part of the dragnet search.
Valid point. It's a different branch and a different issue though. Mails that are already on your server and stored there would be relatively safe. Make sure communication is encrypted.
To receive mail, you could setup Haraka (a very simple NodeJS smtp server)[1] on any unix instance (such as AWS micro). You'll need to set proper MX records for your domain and a few simple configurations. If Heroku would let you specify a port (specifically, 25), you would be able to host on Heroku's free plan. This may put you back at odds by hosting your data on AWS (third-party). Also, you would likely need to setup a POP server to download your messages from the server.
I've been researching doing this for a while, but there's one big caveat that I can't get past- there's no decent server solutions for push mail. For desktop computers there's IMAP IDLE, but all the push solutions Apple's software uses are based on Microsoft Exchange (expensive).
I'm running it on two small sites (< 50 users each) and it works as advertised. The nice thing is, it isn't monolithic - you choose the MTA and web software (in my case postfix and apache) and it uses mysql as the backend.
The webmail interface is the best opensource one I've come across (easily beats redcube) and active sync works fine with iphone 4/5 and android.
You could use a local email program and set it to download then purge your mail from the server. That way it's not in their possession for more than 180 days. But you are then responsible for your own backups etc.
You could use a hosted email service in another country where the american authorities don't have easy access. Europe might be an option. However, as with hosting your own email server, that's only a partial solution: If you communicate with other people, your mail is not only stored in your inbox but also in their outbox. So they'd have to use a mail provider outside the US as well - see the first paragraph.
The best is probably a hybrid solution: Try to educate as many people to use encrypted mail as you can and use a mail server that's located outside the US. It doesn't provide 100% protection, but at least you're not part of the dragnet search.