I have a collection of contacts that do not receive my emails

Running 6.0.22344.0.   Have been using eM for years.  There are 4 contacts, all on the same domain, who do not receive my emails when sent from eM Client.  When I send them email from my phone or the web-based email interface, they do receive them.  The emails sent from eM do not end up in their junk folder either.  How could this happen?

Hello Dean, sorry to see this… Are you able to replicate this issue? What account/mail service are you using with eM Client, are you using any security software on your computer? Are you seeing any errors thrown by the application when you try to sen the message to these recipients?

What mail service or domain host are the recipients using is it a private company email?

Thank you,