According to the Reddit threads they are accepting spoofed emails. This is expected in the current dmarc/spf config. Ask them to change their SPF record from
after reading up on the options, understanding the implications and setting the TXT record TTL's to something like 5 mins until it has been in place for a month, then putting it back to 1 hour or longer. The rua has been in place long enough to know what problems it will cause. Be fearless and cause some problems then fix the problems. psd= may have to be different but only fastmail staff would know for sure.
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Also change the _dmarc record from
to something like: after reading up on the options, understanding the implications and setting the TXT record TTL's to something like 5 mins until it has been in place for a month, then putting it back to 1 hour or longer. The rua has been in place long enough to know what problems it will cause. Be fearless and cause some problems then fix the problems. psd= may have to be different but only fastmail staff would know for sure.