On at least 3 occasions (that I know of), an E-mail message I've sent has not been directed to its recipient(s) by the MobileMe SMTP server. This is not a simple glitch; I've resent the exact same messages several times, and they never make it through in their original form. If I edit the messages and remove certain words or phrases, they do get sent. It doesn't matter whether I use Mailsmith, Mail, or the MobileMe Web interface: messages containing the original text do not make it past the server.
In one case, removal of the phrase 'growing hostility against Frankfurt and Brussels' allowed an E-mail message which had been blocked to be sent. Most recently, an E-mail I was sending regarding the growing unrest in Greece has been blocked.
It's fairly clear to me that Apple is silently filtering outgoing E-mail; no notice is given when a message is dropped. On what grounds they feel it reasonable to do this and using what criteria are not clear to me, but, as far as I'm concerned, there is simply no justification for this policy.
I contacted Apple support about this problem, and the tech on the other end went away for a day and eventually came back and told me the message I wanted to send would now make it through. And it did. But they did not do what I requested, which was to disable the outgoing filtering, because a couple of weeks later, the same thing has happened.
I intend to contact Apple support again, but this will be the last time. I intend to find an independent server and obtain my own domain and services independent of Apple, for the first time in over a decade. This is unfortunate, as I've rather enjoyed having my .mac E-mail address, but given Apple's recent authoritarian tendencies in this and other areas, I no longer see any reason to continue supporting them except where absolutely necessary.