wordpress联系表单7不发送超过7mb的文件附件的电子邮件

I have used a contact form 7 form with an attachment field in one of my wordpress websites. The form is working properly (sending mail) when the attached file size (image) is less than 7mb. But If I attach a image file of more than 7mb, the mail is not being sent. Even any error message is not showing, just the processing cycle icon is rotating. just the processing icon is rotating. But, I have set the limit to 15mb. I have used a contact form 7 form with an attac