Encl:

=enclosure

參考英文信件格式有關(guān)附件的相關(guān)內(nèi)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.