How to delete the words "from the mailbox 139", or how to set them and replace them with other words or numbers?

Teach you to send short messages for free-remove the words "from 139 mailbox"

Everyone knows the email address of 139, which sends 30 short messages and 20 multimedia messages for free every month. The ugliest thing is that the words "from 139 mailbox" are written at the back of the message. I want to remove it!

As long as you regularly check the delay of sending for two or three minutes, you will find that the words of the message are missing, which is equivalent to sending ordinary short messages for free.