Encl:=enclosure"随信附上"参考英文信件格式有关附件的相关内容：The "enclosure" and "CC" lines at the end of a business letter are optional. The "encl.:" line tells the reader that you have included an additional piece of documentation with the letter. The "CC" line tells the reader that you have also sent the letter to a secondary audience.
王子麻麻
