Big technical update

We've just rolled out a pretty hefty technical upgrade to our back-end systems.

• Switched our web servers from apache to nginx (faster)
• Updated from PHP 5.4 to 5.6 (faster, better)
• Enabled IPv6 (faster, better on modern networks)
• Updated to SPDY 3.1 (faster)
• Enabled the HSTS header (safer) - we now get an A+ on SSLLabs tests.

You should find things work exactly as before, just faster and more securely!

The HSTS header means that we now always serve everything over SSL encryption, including mailshot web versions and images. If you are hosting your own mailshot images on an insecure site, this may mean that recipients viewing a web version are either not shown images or see a security warning about insecure content from your site. To fix this, either upgrade your site to use SSL (we can help with that), or move your image hosting onto our servers.