Hi everyone,
I can receive messages and send new messages without any issues. However, when I try to respond to a message I’ve received it looks like everything is fine on my end, shows up in Sent folder, but the person I’m replying to never receives my email. Any tips or suggestions? Does this sound like an issue with eM Client or my email server?
Thanks in advance for your help!
anyone??? I’m at my wits end 
Could be that your message is in the recipient’s spam folder.
Yes sound like the recipients mailbox issue where it has some sort of filtering enabled that’s either going to the spam / junk folder as @Gary wrote or possibly being automatically moved to the trash folder “via a rule”.
So if your email is not in their spam / junk mail or trash folder, suggest to have the recipient add your email address to their “whitelist” and see if they then get your email. Also have the recipient check for any rules or spam filtering possibly setup in their “Mail Client” or “ISP Mailbox” when receiving email.
Thank you for the suggestions. Unfortunately it doesn’t seem like my messages are going to the recipients junk/spam/trash folder. It’s like once they’re out there they are just lost. So frustrating and worried this whole mess is going to cost me my job 
What you could do is reply to one of these messages, then when it has been sent, and a copy is in your Sent folder, go to Menu > Operations and look for any SMTP errors in the Log tab.
If there are no errors, then that indicates that the message has been successfully uploaded to the server. You would then need to contact your email provider and ask their advice.
Have you recently checked your own Junk folder to make sure you have not received any failure notices from your email provider? Maybe they had problems delivering the message and already let you know, but the message ended up in your spam.