Email problem

[#1]

I use Outlook Express 6 as my email client because it's always worked for me, but over the last few days I've had an intermittent problem with incoming mail not being received because the address isn't recognised, or else outgoing is email being bounced back, then  the problem seem to clear itself but next day it's back.  I've checked my email settings and they're OK and I don't know where else the problem might be.
Anyone got any ideas as to what the problem might be?

[#2]

possibly this http://usertools.plus.net/status/archive/1299084257.htm

[#3]

Thanks PP.  I notice the work was done on Thursday, should I still be experiencing problems three days later?

[#4]

You shouldn't
I would raise a ticket

[#5]

I did raise a ticket but they're showing 25hours+ before I get a reply so I thought I'd ask on the forum 'cos I guessed I'd get a quicker response here.

[#6]

Do you get error codes when incoming and outgoing failures occur? If so looking up likely explanations for these might help.

[#7]

@spraxyt
The error message is copied below
The following message to
<xxxxxx@xxxxxxxxx.plus.com> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-'#5.1.0 Address rejected
xxxxxx@xxxxxxxxx.plus.com

the error message included the correctly addressed, but supposedly undeliverable message, as an attachment.
No response as yet to my ticket
I had a text message earlier to tell me that an email sent to me this morning had been bounced but it appears to be working OK at the moment.

[#8]

Are there any headers with the returned message which might give a clue?
With this sort of thing being intermittent it has the hall marks of being a timing problem. Anti-Virus taking too long to pass it on and/or the time-out setting in Outlook too short (Server Timeouts setting on Internet E-mail Settings Advanced tab). I have 2 minutes set there.
Do you use Norton? or AVG and ZoneAlarm?
Was the mail sent to you that bounced from a Plusnet user or external?

[#9]

@spraxyt
I've reset the timeout at 2 minutes
Iuse AVG antivirus Free  version 2011
The bounced message was from an external user
My email seems to be working OK now so the problem whatever it was has gone
Thanks for your time
BC