PlusNet email send error

[#1]

Hoping someone can help me out... I am getting issues when sending emails from my Outlook email client on my PC (uses a PlusNET mailbox). When I attempt to forward emails, to known email addresses, I get deliverable reply from "System Administrator". The body of the messages includes the following...

            "552 5nKEk66xCU8Ck5nKFkUqqP message rejected due to spam or virus. If you believe this is in error please login to your portal or contact your ISP support team."

If I try to send simple test emails, everything seems to be fine. There doesn't appear to be anything odd in the emails which produce the error when I forward them. Is there an issue with PlusNet virus checking of emails currently?

There is now no live chat option and the PlusNet helpdesk support number is currently saying they are "too busy, phone back another day" which is pretty poor.

Many thanks in advance for any help you can provide

Ian

[#2]

I've never used PN's email service but there are other forum members who do and can probably suggest a solution for you, although it might be worth posting this in the 'Email' section of this forum where it's more likely to be read by PN staff.