The ticket says "our emails are going to spam." It is one of the least actionable reports you will ever receive, because "spam" is the observable symptom of at least three unrelated failures, and the fix for one does nothing for the other two.
The useful thing is a triage order. Rule out the cheap, binary, provable cause first, and only descend into the vague ones when you have eliminated the specific one. Most teams do this backwards — they start rewriting subject lines while their DKIM key has been broken for six weeks.
Here is the order.
The three causes
Authentication — SPF, DKIM and DMARC. Binary, free to check, fixable in an afternoon. Either the receiver can verify you sent the message or it can't.
