If the domain in your image is the one that is having the issue, the nameservers are set to:
Based on the IPs of these nameservers, I doubt they are hosted on your Plesk server.
If I query your Plesk server directly, I get the expected result.
dig +short @docklandsstudios.ie docklandsstudios.ie txt
"v=spf1 +a +mx -all"
To correct this you can either:
Update ns1.blacknight.com with the appropriate
Update your domain to use your Plesk server as the authoritative nameservers.
SPF, Plesk & Qmail
Plesk supports both Qmail and Postfix.
If you are using Qmail, your default
TXT records for
SPF likely will be incorrect if a site has a dedicated IP address.
With Qmail, all email is sent from the server's primary IP address (e.g. eth0) -- regardless of the IP assigned to the site.
As a result, the default record:
v=spf1 +a +mx -all
does not include the primary IP address for any site on a different IP.
To correct this, I recommend adding:
v=spf1 ip4:PRIMARYIP +a +mx -all
where "PRIMARYIP" is the primary IP address of the server.
With Postfix this is not an issue since it will route email from the site's dedicated IP address.
In general, I recommend using
ip4: as it eliminates the need for an additional DNS lookup at the destination server.