WordPress memory usage exceeded 32 MB
WordPress peak memory usage: 38.81 MB
Number of database queries: 24

You might receive emails with description “The description includes Send e-mail notification if memory usage reaches threshold setting” and mail content as above. You receive this message because a plugin named TPC! Memory Usage  is installed under your WordPress blog. TPC! Memory Usage allows WordPress administrators to view the current and peak memory usage of the application.

What you have to do is configure your plugins so that they use less memory, increase the memory limit from plugin configuration OR simply deactivate it.