When running yum update and receiving an error relating to sw-msmtp you will need to remove msmtp once done you should then be able to run updates again.
Resolving Dependencies
--> Running transaction check
---> Package msmtp.x86_64 0:1.4.32-1.el6 will be obsoleted
---> Package sw-msmtp.x86_64 0:1.6.2-17031414 will be obsoleting
--> Processing Conflict: plesk-mail-pc-driver-17.5.3-rhel6.build1705170317.16.x86_64 conflicts sw-msmtp
--> Finished Dependency Resolution
Error: plesk-mail-pc-driver conflicts with sw-msmtp-1.6.2-17031414.x86_64
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
Remove msmtp.
rpm -e msmtp
Rebuild rpm base
rm -rf /var/lib/rpm/__*
rpm --rebuilddb
Run Plesk Installer
plesk installer --select-release-current --reinstall-patch --upgrade-installed-components