Let’s say you want to know when people mention your brand in the press.
For this, there are specialized entities (ZeList Monitor in Romania).
But let’s say you want to monitor newsletter appearances.
One simple solution is to create a new email account (GMail is a good start), subscribe in that account to a lot of newsletters (for a good start see the blog of Cristina Chipurici or open any newsletter from Autocritica.ro and browse to the bottom of the newsletter).
Et – voilà! – that’s how you have basic brand monitoring for newsletters.