All of a sudden I am unable to send email - even reply to an email I just received. Incoming mail works just fine, as does the internet. I am running a Mac laptop (PowerPC G4 15", OS version 10.4.11, Mail version 2.1.3). Every time i try sending or replying I get the following error message: "Error - This message could not be delivered and will remain in your Outbox until it can be delivered. Verify that you have addressed this message correctly. Check your SMTP server settings in Mail Preferences and verify any advanced settings with your system administrator" I have done all that. The settings are the same as on my PC, and I can reply to that same message and it will send perfectly on the PC. The firewall is turned off. Any ideas??