Description of problem, how reproducible and steps to reproduce:
After a build of Sendmail from Fedora Development, I noticed

"sendmail[21473]: unrecognized plaintext verifier saslauthd"

in my syslog, because I built Sendmail only with sasl and not with 
sasl2 support.

So I located the problem and found

/usr/lib/sasl2/Sendmail.conf: pwcheck_method:saslauthd

and also:

/usr/lib/sasl/Sendmail.conf: pwcheck_method:saslauthd

I changed /usr/lib/sasl/Sendmail.conf's content to "pwcheck_method:
pam"

and all works fine, now.

Version-Release number of selected component (if applicable):
sendmail-8.12.11-2

Actual results/Expected results:
In the spec file, I saw, that you use the same "Sendmail.conf" for 
sasl and sasl2...maybe you introduce a second "Sendmail.conf" with 
"pwcheck_method:pam" for sasl1?