I am having this exact issue. I bought the game in 2014 and registered it immediately. I did not login or play until recently. I have never been a free account. But I cannot send mail with attachments. I can receive mail. I can take attachments. I can send mail without attachments. But every time I try to send mail with any attachment, I am kicked to the Character Selection screen with Code: 1022:5:1:876:101. I submitted both a Bug Report and Support ticket. I hope this one is figured out soon!