Here's what the user said when they send a large attachment:
An unknown error was returned from the SMTP server. Subject 'Test',
Account: 'moment.net', Server: 'mail.moment.net', Protocol: SMTP, Server
Response: '432 Service temporarily unavailable.', Port: 25, Secure(SSL):
No, Server Error: 432, Error Number: 0x800CCC61
If I use a feature in Outlook Express which splits the file into six
parts, then I am able to send it.
Check your syslog. There should be some additional errors there.
You think it's in the courieresmtpd logging? That's the only place I see
this error code in the source.
Yes. Something prior to that caused a failure to fork and run the submit
process. When that happens, we go into a failsafe mode, and silently defer
all additional mail, for the rest of the session.
The question is why the submit process failed to start.