While configuring a postfix smtp transport to use SASL authentication, I found the following error in the log:

SASL authentication failure: No worthy mechs found

Besides it’s usually related to an empty intersection between client and server supported methods, there’s some chance you’re missing some libs.

Postfix doesn’t handle SASL directly, but uses an interface. If you have the SASL interface but not the proper handler (eg PLAIN) postfix won’t complain at startup, but at runtime!

Moreover, postconf -a and postconf -A won’t give you any issue.

So when you configure sasl, check if you have all the SASL hanlder libraries (eg. libplain.so) – as suggested here

A simple check like the following, can save you some time.
# rpm -qa \*sasl\*

Or you can use babel-tools, a set of perl scripts that provide a configuration file checker ;)