I have similar problem with Windows Live Mail where mail was not sent immediately as it normally is.
When WLM connects to mail.tpg.com.au (184.108.40.206), instead of the mail server sending 220 code, it sent:
451 Temporary local problem - please try later
The mail item stayed in the Outbox.
The mail item was able to be resent manually. Situation seemed to improve later in the evening.