Are you using Posterous ? If yes, then an email might have arrived to your inbox saying “Posterous will turn off on April 30, 2013”.
Posterous was launched in 2008. And last year, twitter acquired it. & mobile app are going to be shut down on April 30, 2013.
And Posterous spaces will not be available for edit or view.

So what will happen to my data ?

You can go and take backup of your data before April 30, 2013, by visiting following backup link
Take Backup of Posterous
You can click on request backup and once its ready, you will receive an email. Then you can download it from as a .zip file.

What else can be done to retain data ?

You can import your posterous data to wordpress. There is a procedure explained nicely on wordpress. You can Import from Posterous.
Just visit the procedure to Import from Posterous to WordPress.

Some important contents from the mail

Here are the steps:

If you want to move your site to another service, WordPress and Squarespace offer importers that can move all of your content over to either service. Just remember: you need to back up your Spaces by April 30.

We’d like to thank the millions of Posterous users who have supported us on our incredible journey. We hope to provide you with as easy a transition as possible, and look forward to seeing you on Twitter. Thank you.

Sachin Agarwal, Founder and CEO