For some destinations just numeric or just alphanumeric SenderID available. So if you have failed message, try re-send it with other SenderID. This true for few operators in Russia - alphanumeric only.
Kindly be noted that Yakoon will block the user's account with no credits or money refund and without notice in case of unauthorized use of the service. As per Yakoon's Terms and Conditions you agreed not to: Transmit through the Service unlawful, harassing, libelous, abusive, threatening, harmful, vulgar, adult, obscene, lottery or otherwise objectionable material of any kind or nature.
We are grateful for our work with you in 2016 and looking forward to working together in the New Year! We are re-designing our system, so next year will be exciting! Thank you for being such a Great Partner!