Not Thunderbird, probably a domain configuration issue to do with southcoaststeel.co.uk if anything. The error message indicates it cannot find a mail server (MX) to handle mail for the southcoaststeel.co.uk domain.

You might like to contact this company via alternate means and give them the error message, as it's likely other customers are seeing the same thing (and consequently missing email sent from other folks too).

Cheers, Dave

Thanks for your reply, Dave, but I have spoken to the company and they say that they seem to get emails from hundreds of people. So you may be right but I am still hoping for a solution. Thanks again.

Chris

If this is a new domain, it could take days for all the needed name servers to get all the DNS records they need. However the registration in 2014 would indicate it is not that new http://www.dnsstuff.com/tools#whois|type=domain&&value=southcoaststeel.co.uk

I am guessing your mail provider has an old name server record without an MX record. Although MX record support for the domain is fairly spotty see http://www.dnsstuff.com/tools#ispCacheLookup|type=domain&&value=southcoaststeel.co.uk&&recordType=MX

They have an MX now, although the domain setup does appear to have other issues like no A record. see http://www.dnsstuff.com/tools#dnsReport|type=domain&&value=southcoaststeel.co.uk

Thank you so much for your help - I now understand why I cannot send South Coast Steel any emails. I will talk to them.

Your assistance is greatly appreciated. Thank you again.

Best wishes

Chris Powell

Chrispen4 said

I can send emails anywhere EXCEPT to info@southcoaststeel.co.uk - when I get a Failed message stating "No valid MX found". Is this a Thunderbird problem or a problem with 1&1 Internet who host my email address? I do hope someone can help me. I need to know how to fix it! Thank you all.