Is this a sudden, new problem or an ongoing one?
=================
Troubleshooting error messages that you receive when you are using OL and OE
http://support.microsoft.com/kb/813514

Disable email scanning by your anti-virus application.  It provides no
additional protection and even Symantec says it's not necessary:

<QP>
Disabling Email Scanning does not leave you unprotected against viruses that
are distributed as email attachments. Norton AntiVirus Auto-Protect scans
incoming files as they are saved to your hard drive, including email and
email attachments. Email Scanning is just another layer on top of this. To
make sure that Auto-Protect is providing the maximum protection, keep
Auto-Protect enabled and run LiveUpdate regularly to ensure that you have
the most recent virus definitions.
</QP>
http://service1.symantec.com/SUPPORT/nav.nsf/docid/2002111812533106

This is a bulk mail error message generated by your ISP. I suggest you
contact them.

Your ISP is saying that too much mail (SPAM) has been coming from your
PC.    If you haven't intentionally been sending a lot of mail (sending
one message to 50 people counts the same as sending 50 messages to one
person each) then your PC may be infected with a SPAM-BOT (a spammer has
installed a program (virus) on your PC to take control of it and send
all the SPAM.)

In the later case, you'll need to clean up your PC.

Dealing with Unwanted Spyware, Parasites, Toolbars and Search Engines
http://www.mvps.org/winhelp2002/unwanted.htm

Spyware, Browser Hijackings and other Antisocial Tricks
http://inetexplorer.mvps.org/darnit.html

Removing Malware
http://www.elephantboycomputers.com/page2.html#Removing_Malware

In either case, you'll need to call your ISP to get your account
enabled.

Try 'smtpauth.sbcglobal.net'. You will have to check "My server requires
authentication", and use your full email address to log in to that server.
It supposedly has higher limits, but if you are sending over 200, or so
email messages in a day, you may need paid email hosting with a bulk email
service provider.

Hi,

After having tried various of methods without improvement, you can
have a try to use special utility to repair your Outlook Express dbx
file. I know one, called Advanced Outlook Express Repair.
Fortunately , It worked rather well for my corrupt Outlook Express dbx
files last time. I think it may be helpful to you. You can download it
from the following address .Its web address is http://www.datanumen.com/aoer/

Alan

Your error was received prior to a change in the way that 'mail.pacbell.net'
operates. On the date of your original post, 'mail.pacbell.net' work on the
basis of limiting access to authorized users by means of an ACL (Access
Control List) containing a list of the AT&T Internet Services (for domains,
such as, 'pacbell.net') IP addresses. The servers also had a message rate
limit at that time which was rather low, based on the assumption that access
was primarily from residential customers.

Commencing April 23, 2008, or so, ATTIS changed the DNS record for
'mail.pacbell.net' to point to a cluster of SMTP AUTH message submission
servers. The change means the following:

Your email client must now be configured for "My server requires
authentication". (New requirement.)

You must use your full email address to authenticate. (Not really new, but
if you had never configured 'mail.pacbell.net' for authenticated access, you
might have missed that change in the way that SBC Internet Services (as
ATTIS was called when that change was made) operates.

Access to the server is now available through port 587. These "changes" are
primarily due to the fact that 'mail.pacbell.net' now points to the same
server cluster as 'smtpauth.sbcglobal.net', which had always worked in this
fashion.

The new server cluster that 'mail.pacbell.et' points to reportedly has a
higher rate limit for outgoing email. Things may not be as dicey now as they
were in the past.

I believe the change was made to facilitate access from wireless hotspots,
which AT&T now provides free on their Express, Pro, and Elite packages. The
option to use port 587 exists to deal with foreign (meaning non-ATTIS) IP
networks which block access to outbound port 25 for spam control.

BTW, as others already pointed out, the erratic nature of the problem was
not due to a problem with MS Outlook Express, and changing your mail client
did/will not solve any problems. I did post a solution for you on April 9,
suggesting that you use 'smtpauth.sbcglobal.net'. However, now that
'mail.pacbell.net' points to the same IP address, that suggestion is moot.

The main thing to remember now is, "SMTP AUTH". Both MSOE and WLM have a
setting on the servers tab: "My outgoing server requires authentication". If
you are using 'postoffice.pacbell.net' to fetch your email, you can just let
the client use the POP3 authentication settings.