What is the reason why the picture of Xiaomi 3 MMS is unclear?

I used Xiaomi 1S, and I didn't use Xiaomi to send MMS, but I think SMS should automatically reduce the picture when sending pictures, because that's what I used to send on my mobile phone, and then I saved traffic. . . Landlord, you can look in the settings, or see if there is an option when sending MMS. It should be a short message thumbnail.