As of June 25th 2016 sandbox orgs no longer support TLS 1.0 encryption. The previously optional critical update “Require TLS 1.1 or higher for HTTPS connections” was auto-activated on this date. Production orgs will be auto-activated on the 4th March 2017.
Inbound API connections requesting TLS 1.0 will receive the error message “TLS 1.0 has been disabled in this organization. Please use TLS 1.1 or higher when connecting to Salesforce using https.”.
For Force.com IDE (Eclipse) users on Java 7 the eclipse.ini file must be modified to add the line below. This is not required for Java 8.
Further information here.