Spool Manager

The Spool directory is also known as "the queue" since it is the place where messages wait to be delivered. Messages in the queue include incoming messages, outgoing messages, and attachments, as well as error messages generated by IMail Server or other mail servers. The Spool directory is also where the IMail Server log files are stored.

Files in the Spool directory are all plain text and can be viewed using Windows Notepad. Note, however, that if you edit a D (data file) or Q file (message awaiting delivery), you could render the file incompatible with IMail Server.

To view the files in the queue, see Managing Messages in the Spool.

Files in the Queue

Files in the queue are on the way in or out. The Number of Tries column shows the number of times IMail has attempted to deliver a message. When this number reaches the number of Tries Before Return to Sender, which is set on the IMail SMTP Services page, the message is returned to the sender as "undeliverable."

When you look at the files in the queue, you can determine what stage a message is in. This is indicated by the first character in the file name and by the file extension.

File Locking

IMail employs a built-in locking system for files in the Spool Directory to eliminate concurrency problems. Locks are created by modifying the first character of a file name and creating a special file in the same directory as the locked file.

Files in the Spool Directory are only locked while critical reads or writes are being performed on the file. Old locks are removed if they are more than one hour old. This means a user may be locked out of accessing a file or a service for up to one hour as a result of a system crash during a critical time period.

It is possible to manually remove a locked file if you are positive that no process is actually accessing that file. One reason for the long time period is to allow for any time required to transmit large files over slow links. For example, the time-out should be long enough to transmit a 2+ megabyte file across a 2400 baud dial-up connection with processing delays caused by the remote end.

Attachments

Attached files also appear in the queue. For multiple attachments, the Windows Explorer naming convention is used. For example, attach.txt, attach(1).txt, attach(2).txt, and so on.

Troubleshooting

Normally, IMail Server cleans up its .tmp and attached files as part of the delivery process. However, as with SMTP, if there is some catastrophic failure during delivery, these files may not get deleted. You can run the Spool Cleaner utility to delete old files. For more information, see Cleaning the Spool Directory.