OpenSSL, AT&T (att) Yahoo passwords, sub-accounts and general 'net security

WOW! I just joined this "Community Forum" less than 10 minutes ago (11:59 PDT 15-Apr-14). First I tried to find a solution without having to take other people's time. I saw:

Troubleshoot your AT&T email (http://forums.att.com/t5/U-verse-email/Troubleshoot-your-AT-amp-T-email/td-p/3900463) and tried to surf to the "Accepted Solution" on that page (http://forums.att.com/t5/U-verse-email/Troubleshoot-your-AT-amp-T-email/m-p/3900465#M1034). When I received that "Solution" page, I was told I have:

Sorry, you do not have sufficient privileges for that action.

Please click the Back button on your browser.

How dumb!

My problem starts with the mating of Yahoo.com (as an email provider) and AT&T as using or mating with Yahoo. The two technologies converge to create multiple problems for me.

I manage several account names and passwords under the Uverse service. Or maybe it's under both DSL and Uverse. Nobody at AT&T can explain this very well to me so far. FYI, I stared with DSL "Elite" and switched, last June to Uverse "Max". so there are several account numbers and names. When I called: 800-288-2020 and tried to speak with an agent, the agent's voice is so thick with a non-English speaker accent that it's too difficult to get phone help. Hence I posting here.

I use a password manager to know passwords. In that manager I have hundreds of passwords. This manager also runs a security check about OpenSSL and Heartbleed. That security check shows only that I have one "Yahoo" password (or account) that is secured from the heartbleed bug and one "Yahoo" password (or account) that is vulnerable to Heartbleed.

When I search the password manager for "Yahoo" I get 49 separate accounts and passwords. I want to fix this, but I every time I change passwords at both/either AT&T - Yahoo, I have problems using my email client named: Thunderbird. In the past, when I have changed password, I have had to forgo using Thunderbird for months at a time.

Here some of the help I need:

Does AT&T use or allow use of passwords with characters (so-called 'Special Characters') such as: "% @ ( # !" ? or only letters and number?

Does Yahoo-ATT do the same?

I believe that I pay for this ISP and it (they) should make my work easy, not as difficult as humanly possible, because AT&T is more concerned about lawsuits, "the bottom line" and other items inappropriate to their vaunted "Customer Service".