The package description for
msmtp-mta documents that it is a wrapper which will pull in
msmtp as a dependency anyway.
This package provides the regular MTA program.
This is somewhat obscure, but apparently means
The package's file listing reveals exactly what it contains. As of right now (version 1.6.6-1) it contains the following files:
(In case you are unfamiliar with Debian packages, the stuff in
/usr/share/doc/mssmtp-mta is just standard metadata for the package, and the
/usr/share/lintian/overrides are specifics for the
lintian package integrity checker, probably to say that it's okay for it to ship the same binaries as some other packages which also implement the legacy Sendmail command-line API.)