商業函件中的信件部份，主要包括從馬來亞各市及新加坡余仁生寄給余仁生（香港）的大量信件，計自 1956年至1968年，共有1,278張，當時按信的來源地及日期用金屬文件夾分成數疊保存。此外還有1956年及1961年從馬來亞和新加坡寄返香港母公司的劃一表格和收據，確認收訖匯款、信單及回條。其他零散信件、便條、賀卡、名片和已拆的信封，也存放在這部份的資料中。

This subseries contains a large quantity of correspondence sent to Eu Yan Sang (Hong Kong) from affiliated branch offices in Malaya and Singapore. There are altogether 1,278 letters and were bound separately according to where they were from and in chronological order in the period 1956－1968. Besides, there are remittance-related correspondence in self-designed standard forms directed to Hong Kong office from Malaya and Singapore in 1956 and 1961 acknowledging receipt of remittance. Other loose letters and notes, greeting cards, business cards and opened envelops are also kept under this subseries.