Notes from the deliverability lab.
Best cold email infrastructure platforms in 2026: 10 providers compared
Honest, hands-on ranking of the 10 cold email infrastructure platforms that actually ship mailboxes at agency scale. Pricing, partner status, DNS automation, dedicated IPs, and what each is best for.
The InboxLee TeamMay 30, 2026 · 14 min readSubdomain vs root domain for cold email: which one protects your main brand
Sending cold from mail.yourcompany.com instead of yourcompany.com is a real strategic call. Here is when each one wins.
The InboxLee TeamMay 23Email warmup tools compared: Smartlead vs Instantly vs Lemlist warmup networks
Three sending tools, three slightly different warmup networks. The differences matter for cohort consistency and how InboxLee reads the curve back.
The InboxLee TeamMay 23Cold email tools compared in 2026: Smartlead vs Instantly vs Lemlist vs Apollo
Four sending tools that dominate cold-email outreach. The honest comparison across cohort sending, reply detection, warmup network, and pricing.
The InboxLee TeamMay 23How to warm up a cold-email domain in 2026: the 30-day playbook
Domain warmup is different from mailbox warmup. The domain takes 30 days; the mailboxes take 14. Here is what to do during each.
The InboxLee TeamMay 23Email greylisting in 2026: what it is and how it affects cold-email delivery
Greylisting is a 20-year-old spam-prevention trick that some receivers still use. It introduces a 5-30 minute delay on first delivery and shows up in your logs as a soft bounce.
The InboxLee TeamMay 23Mailbox naming conventions for cold email: what looks personable and what looks spammy
Mailbox names are a 0.5-second trust signal. first.last@yourdomain.com wins over team@. Here is the full naming hierarchy.
The InboxLee TeamMay 23SMTP bounce codes explained: 4xx, 5xx, and what each one tells a cold-email operator
Every cold-email bounce returns a numeric SMTP code. Most operators ignore them. Reading the codes turns a black-box bounce into a specific problem you can fix.
The InboxLee TeamMay 23MTA-STS for cold email: what it is, how it interacts with TLS, and whether you need it in 2026
Optional in 2026. Not required by Gmail or Yahoo. Still a clean positive signal that inbox providers notice - and InboxLee publishes it by default.
The InboxLee TeamMay 20SPF records for cold email senders: the complete no-fluff guide
What SPF does, why you need exactly one record, the common errors, and what InboxLee configures.
The InboxLee TeamApr 15