However, if the other party really doesn't want you to know, even if you check it, there is no way, because the other party can choose not to send a "read receipt" when reading the letter.
Extended data:
1, automatic reply: If the other party's mailbox is set with automatic reply, you will automatically send an email to his mailbox after sending it, saying that it has been received. This function is set by the other party, as long as it is sent to his email, you will receive a reply.
2. Read receipt: Check "Automatically request receipt when sending a letter" in mailbox settings-sending settings, or check "Read receipt" when writing a letter, so that the other party will prompt to send a receipt after seeing the email.
As long as you promise to send it, you will receive it. This function is set when you write a letter. When the other party sees the email and agrees to send it, you will receive the receipt you want.
4. If you are a Netease mailbox, you can also log in to the Netease webpage mailbox, and then check your recent mail sending records in the self-service query, so that you can check whether it is sent normally.