When enough is it too much?

All email marketing blogs and websites (including this one) give you plenty of advices and best practices for your email marketing strategy.
This list of best practices usually includes (but not exclusively) getting rid of inactive email addresses, segmenting the database and personalizing your email campaigns.

Recently though, I had some of my clients that took these practices one step too far and the outcome was not as good as expected.

Let's start with the segmentation thing: Segmenting is good, but if you segment too much you will come across several issues:
First, the final volume will probably be inferior to what you usually broadcast.
Secondly, this kind of extremely precise segmentation will only have extended value if you are able to target dedicated emails to each segment, it will therefore also increase your creative budget.
Finally, the statistics will be also more difficult to read and analyze.

Then database cleanup: Having a clean database where you remove inactive profiles is a very good practice, but I had a client who's inactive users exclusion list was too tight and during the summer vacation a bunch of active profiles (especially young students, with several months of vacation) where inactivated (of course we reactivated the accounts afterward).

For the last best practice I have no special example except from my own personal experience. If personalizing emails is very good, whenever I receive an email which personalization is too precise and advanced, it kind of frightens me a bit (although, since I work in email marketing I am kind of used to it).

According to me, best practices are like food: necessary but if you get to the excess it ca damage your balance.