Notes from the deliverability lab.
How many mailboxes do you actually need for cold email?
A simple formula based on daily send volume, ramp time, and the 50-per-day Gmail ceiling.
The InboxLee TeamMar 12.com vs .co vs .io: which TLD lands best for cold email
TLD choice is a deliverability signal, a cost signal, and a brand signal. The right pick depends on which you optimise for.
The InboxLee TeamMar 10DNS propagation timelines: when "live" is actually live
Propagation is not instant. Here is how long each step takes and what to expect during the wait.
The InboxLee TeamMar 7Google Workspace vs Microsoft 365 for cold outbound: where each one wins
Workspace and M365 both work for cold email. They differ on cost, throttling behaviour, and partner economics.
The InboxLee TeamMar 4Dedicated SMTP for cold email: when it is worth the upgrade
Dedicated SMTP is overkill for most senders and essential for some. Here is the volume threshold where the math changes.
The InboxLee TeamMar 1JMRP and FBL explained: how to read complaint loops as a cold sender
JMRP and FBL are the only direct complaint signals Microsoft and Yahoo provide. Most cold senders never see them.
The InboxLee TeamFeb 26Reverse DNS (PTR) for cold email senders: what it is and when to fix it
PTR records are usually somebody else's problem. Here is when they become yours.
The InboxLee TeamFeb 22TLS 1.2 (and 1.3) for cold email: why opportunistic encryption matters
Mail in transit should be encrypted. Most providers enforce TLS 1.2 or higher. Here is the operational impact.
The InboxLee TeamFeb 19Mailbox warmup mechanics: what actually happens during the 14 days
Warmup is not magic. Here is what providers see and how they decide your reputation is real.
The InboxLee TeamFeb 15Managed DNS vs registrar DNS: which one to use for cold-email domains
A dedicated managed DNS provider is faster, more reliable, and more reportable than most registrar DNS. Here is the trade-off.
The InboxLee TeamFeb 12