Forwarding Email Account Dropping Emails Without Bouncing Them

I own my domain [url] and have a reseller plan on a shared host [url]I have the DNS on godaddy pointed to the nameservers of reyox and on the Cpanel of my domain at reyox I have a forwarding account [url]set to forward to my gmail account.

To the best of my knowledge this has worked flawlessly for years but recently I have been starting to not receive emails from people. I found out when I wasn't getting replies I had been expecting and when I inquired or called the people instead they told me that hey replied... it's been happening over and over again lately.

When I asked my host last week they replied: "We did clear up some mail issues last night, some issues with the queue processing."

However after that it kept happening and now I am at a loss.

I don't know what's wrong nor how to troubleshoot it... It happened with people that are on all sorts of domains (gmail, aol, personal domains etc) and it happens sporadically...
It's really frustrating because I don't know what else I am not getting considering that every other day I find out about an expected email I didn't get.

The werid thing is that none of the senders whose emails got lost reported that they received a bounce issue...

how I can address this in terms of troubleshooting it and finding a solution?

Is there some sort of email monitoring services like there are site uptime monitoring services?