outdated line in 27.9. SMTP Authentication

[Robert Hsiung]

Dear FreeBSD Documentation Project,

Hi, I've set up web servers before, but never an email server, and the 
Handbook was invaluable, thank you.

I do think one line in:

https://www.freebsd.org/doc/handbook/SMTP-Auth.html

might be outdated. In step 4, I believe the first configuration option:

SENDMAIL_CFLAGS=-I/usr/local/include/sasl -DSASL

should be:

SENDMAIL_CFLAGS=-I/usr/local/include -DSASL=2

See:

https://lists.freebsd.org/pipermail/freebsd-questions/2012-March/239310.html

Thanks again for making this resource available.

Bob