Some mailboxes support source code input, such as QQ mailboxes, and some mailboxes do not. At this time, there is no better way, but to change the mailbox and send it with a supported mailbox.

It is suggested to send HTML mail by QQ mailbox.

If you do a graphic resume or a graphic email, you can use a ready-made network platform (Baidu can find it by searching for a graphic email), which is super simple, highly compatible (this is very important) and efficient. You can try.