Generally good emails will not get blocked but on rare occasions this may happen and so to overcome this you can simply white list their email or domain and make sure an email sender never gets blocked by the spam filter.
First login to your spam dashboard: https://antispam1.webspeed.co.uk
If you need to retrieve login details for your spam quarantine see these instructions
Once you are logged into your spam quarantine dashboard go to “sender whitelist – incoming” in the left menu
On the next page click the “Add whitelist sender” option
A pop up window will appear where you can add in the email address you want to white list, leave the “sender flag” option set to “Apply to both” and add the email addres you want to whitelist in the “Address” box and click Save
If you want to white list all emails from a domain name so all email accounts under that domain will not get blocked you can just add in the domain part. In this example we are using the sender “firstname.lastname@example.org” so we would just need to add in “webpixel.co.uk” then anything @webpixel.co.uk will be allowed through. You only want to do this with domains you trust, obviously you would never want to white list the domain of an email provider like “gmail.com” for example.