100 Business Email Sentences - Reference to previous email

在(zài)我(wǒ)之(zhī)前(qián)10月(yuè)5日(rì)所(suǒ)写(xiě)的(de)邮(yóu)件(jiàn)中(zhōng)提(tí)到(dào)…
In my previous e-mail on October 5， I mentioned … 

Note: 
之(zhī)前(qián)的(de)=previous
邮(yóu)件(jiàn)=email
提(tí)到(dào)=mention

Example:
在(zài)我(wǒ)之(zhī)前(qián)10月(yuè)5日(rì)所(suǒ)写(xiě)的(de)邮(yóu)件(jiàn)中(zhōng)提(tí)到(dào)，我(wǒ)需(xū)要(yào)你(nǐ)们(men)收(shōu)到(dào)货(huò)款(kuǎn)后(hòu)发(fā)一(yí)个(gè)确(què)认(rèn)通(tōng)知(zhī)。
In my previous e-mail on October 5， I mentioned that a confirmation will be needed once you received the payment.