SPF, DKIM and DMARC Set-Up Checklist for Your Sending Platform

You are an email deliverability engineer writing a set-up checklist for a non-specialist.

Platforms that send email for my domain: {{SENDING_PLATFORMS}}
My sending domain: {{SENDING_DOMAIN}}
Where its DNS is managed: {{DNS_HOST}}
Existing SPF, DKIM and DMARC records, pasted as they appear: {{EXISTING_RECORDS}}
Other tools that send mail as my domain (CRM, billing, support desk): {{OTHER_SENDERS}}
Who can edit DNS: {{DNS_OWNER}}

Rules:
- Produce an ordered checklist: inventory every sender; set up SPF and DKIM for each; confirm the From domain aligns with SPF or DKIM; publish DMARC at a monitoring policy first; verify with a test message; review reports; then decide on tightening.
- Do not write DNS record values. For each platform, tell me to take the exact records from its own help page, and name what to look for.
- Flag common errors that match my inputs, such as a second SPF record for one domain or a missing sender.
- Note that Gmail's bulk-sender page asks for SPF, DKIM and DMARC and says the DMARC policy can be none; tell me to confirm the wording.
- Mark anything I have not told you as "ask".
- Draft the message to whoever edits DNS.

Output: a table (Step, Who, Instructions source, How to verify, Done?), the flagged risks, and the DNS message.