For the path in Outgoing Log File= in accounts.ini for the account, make sure you don't use {variable} for parts of the path. Those are somewhat broken. Use a full path like "C:\Users\your_username\Desktop\outgoinglog.txt" (minus the quotes). Did you make sure to edit accounts.ini while Opera was closed?
If that doesn't help, then the problem is probably that Opera doesn't even get that far into the sending process. Do you have an email address set in the account's properties? Are you trying to send to a lot of addresses where it makes the value of the To, Cc or Bcc text field too long (Send button is basically broken in that case)?
If you try to send to your own email address with just "test" in the subject and "test" in the body, does that at least work or at least create an outgoing log file?
Do you have an outgoing server set on the servers tab in the account's properties? Do you have TLS checked with the port set to 465 or 587? Did you try retyping your username and password on the servers tab?