The e-mail issue sounds quite specific; if the problem persists then you should raise a ticket and ask support to investigate. A 503 error is "Service Unavailable" which is rarely returned if something is working properly.
Upgrades to control panels are common and are not supposed to result in downtime so these are not normally advertised. Such upgrades are usually behind the scenes and are run in order to update various facets of the panel for security reasons. If you feel that your control panel is not behaving correctly, due to a possible upgrade or otherwise, you should raise a ticket with support citing all the issues you are having so they can investigate into your account specifically.
Your PHP problems are likely to be due to a move from PHP4 to PHP5 for all H-Sphere customers. There was an
announcement made on the Xilo blog about this. If you wish to be notified of such things then you can
subscribe to the appropriate category on the blog.
Background to the PHP change can be read in
the blog article on Xilo about PHP4 EOL (end of life)