You just need to re-install the module following the instructions in README.txt. You can get the add-on from the customers area.

Just overwrite or add new .php files and templates. New options introduced at the bottom of addon_pmail_options.php should be pasted in your older options file as well (do not forget to set up $Tpmb setting). If you have mySQL functions (not flatfiles), you also need to create 'minibbtable_pmessages_blocked' table and enhance 'minibbtable_pmessages_settings' table with the following command:

alter table minibbtable_pmessages_settings add column blockedtotal int(5) unsigned not null default '0';

It is not needed to re-create the data storage schema - all older data should be kept.

Any message on forums could optionally include "Report message" to admins link, and this report will be sent like the current feature of "PM report" works.
Yeah! I need this. With a few hudred posts every day on my forum I am unable to read every post. So users can help in moderating forum in this way. Hopefully, pressing on "Report to admin" will automatically insert the link to the message and some custom text like "Please check this message" into letter's body.

With a few hudred posts every day on my forum I am unable to read every post.

Maybe you could use some moderators if they would be willing to help ;)

Maybe you could use some moderators if they would be willing to help ;)
I have moderators, but they are not always brave enough to delete bad posts. So this "one click" reporting thing would be a very good addition to moderators system.

I will update the add-on next week and it will include this feature, which already may be checked on minibbtest.

That's great - I will give it a try too (after re-thinking and testing it on the test forum :).