Cold email in 5 minutes

New to cold email? This page is the whole picture in five minutes. Every setup that works has the same four parts, and EmailShield is part 4: the last check before anything is sent.

Part 1 Infrastructure Maildeck Domains and inboxes you send from Part 2 Sequencer Instantly, PlusVibe… Sends emails and follow-ups Part 3 Leads LeadSonar The right people and their emails Part 4That's us Verification EmailShield Removes bad addresses first

Part	What it does	Who provides it
1. Infrastructure	The domains and inboxes your emails are sent from, set up and warmed up so they can send safely.	Maildeck, our sister product
2. Sequencer	Sends your emails and follow-ups on a schedule, spread across your inboxes.	A tool you sign up for yourself, such as Instantly or PlusVibe
3. Leads	Finds the right people and their work email addresses.	LeadSonar, our sister product
4. Verification	Checks every address before you send and removes the ones that would bounce.	EmailShield — that’s us

In one line: LeadSonar finds the people, EmailShield cleans the list, your sequencer sends the emails, and Maildeck gives it all somewhere safe to send from.

Why verification can’t be skipped

When you email an address that doesn’t exist, the email bounces: it comes back undelivered.

Email providers like Google and Microsoft watch your bounce rate. Lots of bounces tells them you’re sending to a list nobody checked, which is what spammers do. Your sender reputation drops, more of your emails land in spam, and in bad cases your domain ends up on a blacklist that many mail servers refuse outright.

The domain is the expensive part to lose: it took weeks of warm-up before it could send. Verifying a list costs far less than replacing a burned domain.

Keep bounces under 5%

If a campaign’s bounce rate goes above about 5%, pause it and clean the list before sending more. Most teams aim for under 2%.

Why every list needs it, even a good one

• People change jobs every month. An address that was valid when the list was built can be gone by the time you send. Verify the week you send, not when you build the list.
• Every bad address wastes a sending slot. Each inbox can only send a few dozen cold emails a day. A slot spent on an address that bounces is a slot not spent on someone who could reply.
• Some addresses are traps. Spam traps and abuse desks exist to catch senders who don’t check their lists. EmailShield flags the ones it recognises so you can leave them out.

Words you’ll see a lot

A bounce is an email that comes back undelivered. A catch-all domain accepts mail for every address, so a single mailbox can’t be confirmed either way. Sender reputation is how much the big email providers trust your domain and inbox. The Glossary has the rest.

What to read next

• Your first list in 10 minutes — upload a list and download the clean version.
• Reading your results — what safe to send, risky and invalid mean.
• Maildeck’s guide covers infrastructure in depth: docs.maildeck.co.