If you know the name of the recipient, search them online and get information on their background and professional experience. You may find ways that you can make your subject line stand out by appealing to them directly.  If the recipient has a LinkedIn account, this can be a good place to find information on their professional background. Reading any articles the recipient has written will also help you prepare for the interview or give you information to add in a follow-up email. If you know someone who works for that employer, or if someone recommended you apply for the job, mention their name in your subject line. This will help you stand out from other applicants.  For example, you might use "CV Recommended by Star Butterfly: Marco Diaz for Product Developer." If someone recommended you for the position, but that information at the beginning of the subject line. You want it to be the first thing the recipient reads. Generally, you want to keep your subject line brief. However, if there's something special about your background or experience that makes you uniquely qualified for the position, briefly point it out in the subject line. For example, you might write "CV: Marco Diaz for Product Developer, 20 Years Experience." While you may already know to proofread your email, the subject line often gets overlooked. This can be a serious mistake because the subject line is the first (maybe only) thing the recipient will see. Make sure there are no spelling mistakes or typos. Double-check proper names – even your own – to make sure they're spelled correctly.

TL;DR in Indonesian:
Cari tahu siapa penerima surel Anda. Cantumkan nama orang yang sama-sama dikenal, jika mungkin. Tambahkan kualifikasi terbaik Anda untuk posisi tersebut. Baca ulang subjek surel yang ditulis secara saksama.