Emailing sending error

Hello Experts

A query, I do not know how to classify it as an error and or much control of the mail servers to which an email campaign is sent.

Let me explain: email campaigns are being carried out, but when the email reaches the recipient, the images are not displayed.

And there is a message that says something like: Click here to download or view the image

On the one hand, I think it is because emails are sent to corporate emails and there may be restrictions, but the user tells me that it also happens when it is sent to a gmail account, etc.

Grateful with your answers

Elio C