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Cold Email Deliverability Checklist for B2B Outbound (2026)
Author:
Pablo Jiménez de Parga Ramos
Date:
To keep B2B cold email out of spam in 2026, authenticate every sending domain, keep spam complaints under 0.3%, send from separate warmed domains and test inbox placement every day. throxy runs this for its clients: it sends from separate domains that protect your main brand, rotates across more than 150 mailboxes and multiple IPs, warms every mailbox for two weeks before launch and tests placement daily (deliverability).
Published by throxy. Outside points link to their source and were checked on 14 November 2026. Last updated: 14 November 2026.
What Gmail and Yahoo require
All senders to Gmail need SPF or DKIM, valid forward and reverse DNS (PTR) records, a TLS connection, and a spam rate in Postmaster Tools below 0.3% (Google).
Senders of more than 5,000 messages a day to Gmail also need SPF, DKIM and DMARC, with the From domain aligned to SPF or DKIM (Google).
Google requires one-click unsubscribe for marketing and subscribed messages from those bulk senders (Google).
Yahoo asks bulk senders for SPF, DKIM and a DMARC policy of at least p=none, a one-click list-unsubscribe header, and unsubscribes honoured within 2 days (Yahoo).
The checklist
Send from separate domains. throxy runs campaigns on domains such as trythroxy.com and getthroxy.com to protect the core brand (deliverability).
Authenticate each domain with SPF, DKIM and DMARC (Google).
Warm every mailbox before launch. throxy warms for two weeks, then keeps warming in the background (deliverability).
Spread volume. throxy rotates across more than 150 mailboxes and multiple IPs, and pauses a mailbox that shows fatigue (deliverability).
Match provider to recipient: Google to Google, Outlook to Outlook (deliverability).
Vary every message. throxy varies each send with Spintax to avoid content fingerprinting (deliverability).
Test inbox placement every day and keep checking domain and IP reputation across providers (deliverability).
Keep complaints below 0.3% and honour opt-outs fast (Google, Yahoo).
UK rules for B2B email
You can email corporate subscribers without consent under PECR, but you must not hide your identity and you must give a valid address to opt out. Sole traders and some partnerships are treated as individuals (ICO).
Why timing matters too
Infrastructure gets you to the inbox. throxy built Kairos, its cold email infrastructure, around timing, so emails go out when buying signals suggest the moment is right (Kairos). For the wider argument, read the hidden war for deliverability.
FAQ
Should I send cold email from my main domain?
throxy does not. It sends from separate domains so any deliverability issue stays away from your main brand (deliverability).
Do I need to set up domains and mailboxes myself?
With throxy, no. It manages domains, mailboxes, data and calling end to end (what working with throxy involves).
