Email Not Arriving To Customers Email Account

There are different reasons why an email address doesn't arrive.

Information Needed To Complete Task

Sender Email Address

Recipient Email Address

Time and Date email was sent

optional: Email header information if available with error information


Ticket from customer:

An accountant is trying to contact us via:

They have sent us a couple of emails now, however we aren’t receiving them. They have just tried emailing us on our other email ( and it has came straight through. Do you know / could you please find out if or why there is a block on this email getting through to us?

Step 1 - Find which Server Their Hosting Account is on

Go to WHMCS and find which server their account is on.


Step 2 - Go to WHM of that server

Go to WHMCS Connect


Then click on the correct server.


Step 3 - Go To Mail Delivery Reports

Click in the search box and enter - mail delivery

The option will appear in the left menu and click on it


Step 4 - Try and locate the email


Try entering the recipient email address - in this case they have only provided the receiving email address.

Enter a date range that captures when they said they tried to send it.



Try entering the sender email address. In this particular ticket we don't have this information but we could ask for it


Looking at the result we can see it says:

Deferred due to greylisting. Host: '' From: '' To: '' SPF: 'unchecked'

What is happening is that this email has arrived on our server and because they have configured their SPF incorrectly then our server thinks its spam.

It has greylisted the email address. If they keep trying to deliver the message, eventually our server will let it thru. Spam email usually try just once, where genuine email usually try several times before giving up.


Step 5 - Check The SPF of the sender email

If we do a SPF check on the sender domain we can see more of what the issue is.

In this case the domain says that emails from: or

ip or


are not spam.

Our greylisting service has falsely blocked this email because the IP its come from is allowed to send emails.



Step 6 - Go to Greylisting

As its correct we need to whitelist the IP range.

Search for "greylisting" in the search box and click on trusted hosts.


Step 6 - Whitelist IP

Enter the IP addresses so we can whitelist them.

Click Add once done.

In future emails from these IPs will be allowed in.