After reading the email, I suddenly felt weak and was about to collapse from my knees.
After reading an email that I had not expected, I felt the power go out of me and wanted to just sit down.
ご質問ありがとうございます。
① "After reading the email,"＝「メールを読んだ後、」
"I suddenly felt weak"＝「突然、力が抜けて」
"and was about to collapse from my knees."＝「膝から崩れ落ちそうになった。」
② "After reading an email that I had not expected,"＝「期待外れのメールを読んで」
"I felt the power go out of me and wanted to just sit down."＝「力が抜けて、ただ座りたくなった。」
ご参考に。
アメリカ合衆国 
