If you want to serve a web site, the [email system](email) and [instant messaging](XMPP), the server need to stay turn on all the time, 24h/24 and 7d/7.
Self-hosting results availability of the server to users hosted and/or to externals people consulting it.
Problems can happen making server unavailable: power outage, loss of access to the Internet…etc.
If you use the [email system](email_en), and your server is unavailable, emails for the server will be sent under 3 to 7 days.
#### Self-hosting contraints
* The rate of transmission information is low. In ADSL case, it’s often approximately 1/10 related to the rate of reception. For instance: 1 Mo/s of reception and 100 ko/s of emission;
