这个前半句语法对么?

改成,if the e-mail happens to be missed by someone..如果有人偶然间(不小心)造成电子邮件的丢失...

if it happens to be someone misses the email
语法错误。

if it happens 后面接的是从句，而不是someone。
所以应该为：if it happens that someone missed the email......

it happens to be me. 意思是：碰巧是我。

。。明显someone前面的that可以省略，一样是跟的从句。
没觉得有什么问题……

我觉得不对， it happens意思是：碰巧是..., 发生的情况是... 可以这样使用：
1.it happens that +从句
2.如果要用it happens to be，后面只能是名词

if it happens to be that someone missed the e-mail

sounds right to me