email bounce error 'SPF Permanent Error: Too many DNS lookups'
An SPF record is mis-configured. See:
If the report was about your Linode, you need to fix this with the DNS Manager. My (working) SPF record looks like this:
v=spf1 a mx a -all
Here's how to decode it: https://www.zytrax.com/books/dns/ch9/spf.html
If the report is about another domain, all you can do is beg the sysadmin there to fix it.
SPF records are limited to 10 DNS lookups - I've seen this same error from Gmail.
For example: "a:some.host.com" in an SPF record results in a lookup for the IP address of "some.host.com" - that's 1 DNS lookup.
Including other SPF records (include:some.domain.com) is another source of DNS lookups.
Check your SPF record and see how many parameters would result in DNS lookups, and substitute IP addresses where possible.