Warning: You are best to use a (transactional) SMTP provider and use their SPF DKIM and dmarc.
See: https://www.publicdocumentation.com/email/ for more information.
Cluster 1 (the Netherlands – Brabant)
include:_spf_c1.wpmanaged.nlCluster 2 (the Netherlands – Rotterdam)
include:_spf_c2.wpmanaged.nlCluster 3 (the Netherlands – Brabant)
include:_spf_c3.wpmanaged.nlLocation 4 (Germany – Frankfurt)
include:_spf_c4.wpmanaged.nl