Specifies the number of seconds to wait for the `` $sendmail'' process to finish before giving up and putting delivery in the background.
Mutt interprets the value of this variable as follows:
number of seconds to wait for sendmail to finish before continuing
wait forever for sendmail to finish
always put sendmail in the background without waiting
Note that if you specify a value other than 0, the output of the child process will be put in a temporary file. If there is some error, you will be informed as to where to find the output.