"귀사의 관심과 협조에 서신으로 나마 인사를 대신드립니다." => 귀사의 관심과 협조에 서신으로나마 인사를 대신 드립니다. => We would like to express, albeit in a letter, our gratitude for your interest and support. (faithful to the original) => We would like to express our gratitude for the interest and support you have shown us. (more likely in real world) - 귀사의 관심과 협조에: for the interest and support you have shown us. - 서신으로나마: albeit in a letter(even if it is only in a letter and not a full face-to-face meeting). - 인사를 드립니다: we would like to express our gratitude; we thank you.