Netzero slowed by blocked ads

[netzero1]

I am using Adblock Plus 1.9.3 with Safari 9.0.1 in Private mode in OS X 10.10.5 when doing email with Netzero. ABP works well until the number of blocked ads gets to be more than a few hundred. Then Netzero slows to a crawl, making it so that typing a few words takes forever and new emails take forever to load. If I reload Netzero it is good until the number of blocked ads goes up again. I am hoping there is some "cure" for this? Thank you.