I think that you mean Netscape Webmail, i.e. @netscape.net account.
This type of account is accessible only iin the later Netscapes.
By the way, I still have 4.8, and comparing its filters and Netscape7.2's there is no difference.
The biggest difference is that you can not only setup Webmail in NS7.2, but you can have just about an unlimited number of accounts in a single User profile. I have 12 of mine and my wife.
As you know you can set up only one POP account at a time in 4.8.
But, you are correct, most places of work have made no effort to introduce anything past 4.8, mainly because the complexities 7.2 are more than an IT person could handle, and, there have been so many updates since 6.0, that it would drive them crazy. 7.2 cannot be handles the same way as 4.8. But, 4.8 is the end of the line, and a number of websits are not accessible by it.
Also, 7.2 has Junk mail(spam) controls which could replace your filter.
I have about 30 filters in my 4.8 account. I have fewer than 10 in my twelve NS7.2 accounts, combined.
But, if you don't want to think too much, and you use a single mail account, and use it primarily for mail, 4.8 is great.
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; rv:1.7.3) Gecko/20041001 Moonelk/0.10.1