Delay in receiving external email

[mtnhigh]

I have been noticing lately that at least once a week, I get calls from my users complaining about them not receiving external email and/or a deplay in receiving external email. I have checked the mx record and it is correct, Where else can I check, and what could the problem be? My users states that it comes from a variety of sources, yahoo.com, aol.com hotmail.com and the such. I ran a dnsreport on my domain and I receive the following fails/warns. Could this have something to do with it?

Open DNS servers-fail
Missing (stealth) nameservers-fail
Missing nameservers 2-fail
Nameservers on separate class C's--warn
Single Point of Failure--warn
Stealth NS record leakage-fail
SOA MNAME Check--warn
SOA EXPIRE value--warn
SPF record--warn

The users dont receive a delievery report, the email never gets deliveried, in my case I sent a yahoo email to myself yesterday morning and have yet to receive. I forgot to mention we dont host our DNS, it is hosted by a third party

thanks

 

[Asim2]

looks like the sender can't find your smtp(exchange server) this must have due to DNS. Check this with your ISP. If the sender can't find the exchange server, all e-mail will be lost in the space. You should also check your delivery queue on your Exchangeserver......