CF Mail Spooler Woes...

We have been having some issues with our mail server recently. Mail hasn't been going out and this is what we noticed in the logs:

"Error","scheduler-4","06/03/08","10:33:24",,"Could not connect to SMTP host: xxx.xxx.xxx.xxx, port: 25; nested exception is: java.net.ConnectException: Connection refused: connect"
javax.mail.MessagingException: Could not connect to SMTP host: xxx.xxx.xxx.xxx, port: 25;
nested exception is:
java.net.ConnectException: Connection refused: connect

and

"Error","scheduler-1","04/02/08","03:30:56",,"A problem occurred when attempting to deliver mail. This exception was caused by: coldfusion.mail.MailSpooler$SpoolLockTimeoutException: A timeout occurred while waiting for the lock on the mail spool directory.."

From what I found, this occurs for two reasons:

1. Bombage from sending a huge email
2. Insufficient disk space

Reference: http://www.talkingtree.com/blog/index.cfm?mode=entry&entry=67FD4A34-50DA-0559-A042BCA588B4C15B

We did notice a message the other day claiming that we were running low on disk space.
There is a recent hotfix from Adobe that supposedly helps this that was released in April '08 that supersedes a previous hotfix in this area. That hotfix can be found here: http://kb.adobe.com/selfservice/viewContent.do?externalId=kb402001&sliceId=1
We applied the hotfix today and cleared some disk space so we'll see happens.

Update: after getting our hands dirty today, KP found that there was a backup of 10,000+ emails in the inetpub/mailroot/queue directory. Something is getting hosed at that level. He found this by telnet'ing to the server's port 25 and sending a message. It told him that the message had been queued for delivery. He never did get the message which told us that the bottleneck was at the queue. We've got a ticket opened up to check it out.