problems sending email this morning - any ideas?

[clarebear]

The e-mail system was unable to deliver the message, but did not
report a specific reason.  Check the address and try again.  If it still
fails, contact your system administrator.
    < c2beaomr06.btconnect.com #5.0.0 SMTP; 550 SC-001 (COL0-MC1-F48)
Unfortunately, messages from 213.123.26.184 weren't sent. Please contact
your Internet service provider since part of their network is on our
block list.

Error message above was received this monring - I have tried to send several emails to several different addresses - they all come back with the same message.  BT is our ISP and our email is through BT too so why are my emails being blocked?

[clarebear]

everything has been working fine up until now and we haven't changed anything so I am assuming this is a BT problem?

[kuerten]

nslookup 2beaomr06.btconnect.com
Server: vnsc-bak.sys.gtei.net
Address: 4.2.2.2

*** vnsc-bak.sys.gtei.net can't find 2beaomr06.btconnect.com: Non-existent domai

An open DNS 4.2.2.2 what able to recognize the MX record. There's your problem. Good luck.