We have recently discovered that e-mails we have sent to friends with addresses that end @Yahoo.co.uk have NOT been received, despite Thunderbird confirming the messages were sent and we have not received any Undeliverable message alerts. Once we were aware of the problem we sent 4 e-mails to one of our friends and they only received 2 of them, another friend was sent 7 e-mails and only received 2 of them! What is annoying us is that we cannot tell when or if an e-mail has really been delivered to a Yahoo.co.uk e-mail address. We run a small business and we cannot afford to loose business because our e-mails don't get through! To date we have only become aware of this problem with Yahoo e-mail addresses, but maybe it affects other servers? Please can you help - what can we do to be certain our e-mails really do get through? Many thanks, Ian Lister == URL of affected sites == http://yahoo.co.uk