Strange one this:
Moved my O2 SIM card from another (older) HTC phone where SMS worked with no problem at all, to HTC HERO, where it says that the messages are sent but they never arrive with the recipient.
I've used the supplied SMS system and the free App HandCent SMS - both show the message as sent but no one receives them.
Incoming SMS are fine- appears to be no problem there.
Phone works ok for outgoing and incoming calls (apart from approx 30% worse reception than the previous HTC).
Does anyone have any ideas? Could O2 have a block on SMS messages because of a new IMEA number ?