zhè / fēng / xìn / de / mò / wěi / xiě / zhe / fù / bǐng / dīng / biǎo / shì / yuè / hòu / fén / huǐ

这封信的末尾写着“付丙丁”，表示阅后焚毁。

The end of the letter said “burn after reading,” meaning it should be destroyed after being read.