[nznog] Emails to xtra addresses not being delivered

My server generates emails for about 150 members of a choir. 30 of these have xtra addresses, and since the change to yahoo, these are not being delivered. All other addresses work OK. The xtra addresses were OK before the yahoo bubble started up. I receive no notification of non delivery. Can anybody tell me what I need to do to get these emails accepted by the xtra servers? Vaughan Chetwynd 968c Tauwhare Road RD4 Hamilton phone 07 824 0983 mobile 0275 657 724