Under V8 sendmail, the Timeout.queuewarn option (Timeout) can specify an interval to wait before notifying the sender that a message could not immediately be delivered. To keep track of whether such a notification has been sent, sendmail stores the state of its EF_WARNING envelope flag in the qf file. If that flag is set, notification has already been sent.

Error mail messages sent by sendmail can occasionally be queued, rather than immediately delivered. The Timeout.queuewarn option notification should not be sent for such mail. If such mail remains in the queue too long, it should be canceled rather than bounced. V8 sendmail saves the state of the EF_RESPONSE envelope flag in the qf file. If that flag is set, the message is an error notification.

Beginning with V8.8, sendmail also records the state of the EF_HAS8BIT flag (the message body contains 8-bit data) and the EF_DELETE_BCC flag (delete empty Bcc: headers, Bcc:).

All envelope flags are listed in Table 16-6 of -d2.1. The F line is used to save envelope flags for later restoration. Its form looks like this:

Fflags

Here, the flags are any combination of those shown in Table 11-7.

Only the letters listed in the table are recognized. Other letters are silently ignored. Note that these flags might be done away with in later versions of sendmail and new flags might be added without notice.

For security protection, V8 sendmail rejects and logs the following flag sequence:

From
     
    a space here

See Section 11.5.5 for more information about this.