Outlook breaks sent file, how to fix it?

Question

Email

Tell me where to look and fix, I send a PDF file with a poor connection to 2G Internet, the letter hangs in the sent ones and goes broken, it can come to someone I send, about 10-15 letters and everywhere the file is of different sizes and the broken one does not open.
Problem in the client or mail server settings?
Someone faced such a problem?

Answer 1

1. Is your mail server or third party?
2. Try to zip the pdf file.