E-mail by mobile phone, attachment 20m. Do you want to deduct 20m traffic? There are attachments in the received e-mail. Do I have to deduct the flow if I don't open the attachment?

If you send an e-mail, the traffic exceeds 20M, because the e-mail itself still has a certain number of bytes. If the received is not opened, the traffic of the attachment 20M will be removed, but some traffic will still be generated. Traffic is not equal to the size of text, it is the sum of uploading and downloading in the network. As long as you open a web page, even if you don't refresh it, there will be a network traffic called regular handshake, of course, very little.

I hope I can help you!