Due to a change at the organization, handover to the new successor wasn't completed.
There was a reshuffle at the organization and in the confusion an email from you wasn't forwarded to my successor.
"Due to a change at the organization,"「組織変更のせいで」"handover to the new successor wasn't completed" 「新しい後任者に引継ぎ出来てませんでした」。
"Reshuffle" とは組織・会社のコンテキストでは「入れ替え」「人事異動」のことです。"in the confusion" 「その混乱の中で」"an email from you wasn't forwarded to my successor" 「お客様のメールが後任者に届いていませんでした」。
ご参考になれば幸いです。
イギリス 
