The contact list you are sending to is configured to hide list recipients. Many email systems add an Apparently-To header to messages that only have BCC recipients. This header, if added, will list all of your recipients in your message. To avoid this, you should add at least one To: or CC: recipient.
Mae'r rhestr cysylltiadau rydych chi'n anfon ati wedi ei chyflunio i guddio'r rhestr derbynwyr. Mae sawl system e-bost yn ychwanegu pennawd Apparently-To at negeseuon sydd â dim ond derbynwyr BCC. Os ychwanegir y pennawd hwn, fe welir yr holl dderbynwyr o fewn eich neges. I osgoi hyn, dylech ychwanegu o leiaf un derbyniwr At: neu CC:.