How can I specify the "sendmail" program for git-send-email?

Hi, experts

I read the git-send-email manual and find the --smtp-server option can specify the sendmail-like program to send mail.

Then I use this option in command line --smtp-server=/usr/bin/msmtp This works.

While I found it not very convenient to write the option on command line every time, then I wrote it in the .gitconfig file in my home directory.

[sendmail]
	smtpserver = /usr/bin/msmtp
	smtppass       = 123456
	smtpuser       = weiyang@linux.vnet.ibm.com
        smtpserverport = 143

While this time I don't use the --smtp-server option in command line. 

And seems this time, it doesn't use the msmpt to send mail, since this time it fails.

Then my second approach is not correct?