Problem of displaying e-mail on MAC reception

Hello, I have a problem with sending my emails, some appear distorted on some inboxes. Also, some recently added email addresses do not receive e-mails and are marked with a red cross. how to do ?

Emails with a red cross showing simply means that these email addresses have not being confirmed. Remember, phpList operates on the premise that the user must confirm they agree to be subscribed, as is a legal requirement in most countries these days.