DPI and eMail blocking

The more I use wireless Internet access, the more things I stumble over how network operators use Deep Packet Inspaction (DPI) to 'shape' use to their liking. After having been blind charged for eMail in the past and having seen reports of network operators modifying email signaling exchanges to prevent encryption from kicking in, this time I am blocked from receiving eMails.

My current mobile Internet access via a prepaid SIM from Orange in France contains unlimited Internet access and 10 MB (yes, a mere TEN!) to access my email via POP3 or IMAP. I have no idea how I could have stepped over this limit since I am only days in the monthly subscription cycle and all emails downloaded to the mobile are capped at 15 kb. However, one morning I could no longer poll my mailboxes.

Profimail on my N95 crashes as soon as I attempt to access my mailboxes and the Nokia email client reports that the connection to my email provider has failed. Over a Wifi link, both programs can access my email just fine. So I turned to Wireshark to check what is going on and saw that when connected via Orange, the TCP connection requests on the port numbers reserved for POP3 and IMAP are not discarded, as I would have expected it, but immediately answered with a RST (Reset) packet. Note that this packet must have been originated by the DPI device. Looks like Profimail doesn't handle rejected connections gracefully and decides to exit.

Apart from the technical glitch that this provokes, I don't think Orange is doing itself a favor by just blocking incoming eMail. They should have at least sent me an SMS saying that my monthly transmission volume for email has been exceeded and that I shouldn't be surprised that it has stopped working. They could even use it as an upsell opportunity to open the email gate again for an additional charge after sending a text message with a certain content. I'd be happy to pay even if I don't know how I stepped over the limit. Without this option I am now stuck to the mobile webmail interface of my mailboxes while in France, which is a bit uncomfortable. The average user, however, will just be turned off by such a behavior and will probably turn away from the service entierly.

Also, they should offer a web interface that shows me when an how I have spent 10MB on emails in just a couple of days. I am really puzzled.