How to send effective emails (and avoid SPAM)? A step-by-step guide
How to send emails without landing directly in spam?
Do you have an email address database, an idea for a message, and want to launch a campaign? Before you click "Send," learn how to prepare the technical side of your mailing to avoid burning your account, domain, and reputation.
Hello! If you've found your way here, you probably have a great email address database and a message idea, and you're wondering: what next? How do you technically send it without ending up in the SPAM folder of a potential client?
Many beginners think it's enough to dump a thousand addresses into the BCC field of their Gmail and click "Send." Spoiler: that's one of the quickest ways to get your account blocked and your domain burned.
True cold mailing requires preparation, but don't worry—you don't need to be a Silicon Valley programmer to understand the basics.
mailing isn't just about the message content. The server, IP reputation, DNS, sending speed, database quality, and pre-campaign tests all matter. Without these, even the best offer can end up in spam.
1 VPS Server and Port 25 — how to choose a machine for sending?
Let's start with the basics. You won't send a professional campaign from a regular hosting plan for $50 a year, where you keep your company website or blog. For controlled sending, you need your own machine, a VPS server.
A VPS, or Virtual Private Server, is a private piece of a server in the cloud that works for you 24/7. This is where you can set up the environment for sending, mail configuration, testing, and campaign management.
Clean IP
If you get an IP address that someone else previously used for spam, your campaign might face problems from the start. That's why IP reputation is crucial.
Open Port 25
Port 25 is used for SMTP communication between mail servers. Many cheap providers block it by default.
Ability to set rDNS
A professional VPS provider should allow you to set up a PTR record, also known as reverse DNS.
Provider's policy
Not every provider tolerates bulk email sending. It's worth checking the terms and conditions and support's reaction before basing your campaign on it.
2 Sending Script — how to spread out the email queue over time?
You have the server and a B2B company database. What now? You don't send a thousand emails in one second. When Gmail, Outlook, or other systems see a sudden burst of messages from a new source, algorithms quickly become suspicious.
The golden rule is: sending should look natural. Instead of one big blast, it's better to spread it out over time: small batches, pauses, gradual pacing.
Small batches instead of one blast
Don't send the entire database at once. It's better to send gradually, for example, a few or a dozen messages at specified intervals.
Sending queue
A sending script or email system should manage a queue, which is a list of messages to be sent at a controlled pace.
Control and pauses
Sending needs to be monitored. If bounces, errors, or technical problems occur, it's better to halt the campaign than to burn the domain.
3 SPF, DKIM, and DMARC — the holy trinity of deliverability
If you want mail servers to take your message seriously, your domain needs a technical ID. Without it, even the best company database won't help, as messages might bounce off filters.
SPF tells recipient servers: "this specific server is authorized to send messages on behalf of this domain."
DKIM confirms that the message has not been altered en route and genuinely originates from an authorized source.
DMARC specifies what to do with a message if SPF or DKIM don't align: pass, mark, or reject.
In practice, configuration involves adding TXT records in your domain's panel. This isn't magic — these are a few technical entries that increase trust in your mailings.
4 rDNS / PTR Record — the invisible business card of your server
SPF, DKIM, and DMARC are not all. There's another detail that trips up many people: rDNS, or reverse DNS, also known as a PTR record.
Classic DNS translates a domain name into an IP address. Reverse DNS works the other way around: the recipient server checks if your IP address points back to a sensible hostname, e.g., mail.yourdomain.com.
One-way DNS
The domain points to the server's IP, meaning, for example, mail.yourdomain.com leads to a specific IP address.
Two-way rDNS
The server's IP points back to the hostname. This is an additional credibility test for mail systems.
And here's the catch: you usually don't set up the PTR record in your domain panel, but in your VPS panel or through your server provider's support.
Hello, please set up the rDNS/PTR record for my server with IP address [YOUR IP] to: mail.yourdomain.com
5 Anti-spam tests — Mail-Tester is your friend
Before sending a campaign to your database, test your configuration. Never shoot blindly, especially if you're working with a selected group of companies.
One of the simplest tools is Mail-Tester. You go to the website, copy the generated test address, send a message to it, and after a moment, you receive a report evaluating the configuration on a scale of 0 to 10.
- Checks basic DNS settings
- Shows problems with SPF, DKIM, and DMARC
- Evaluates elements affecting the spam score
- Helps detect errors before actual sending
6 Blacklists and IP Reputation — steer clear of them
Even if you have correct DNS records and a good server, everything can crumble due to reputation. Both IP and domain have their history with mail providers.
If your messages frequently hit invalid addresses, generate bounces, or are marked as spam, your reputation drops. In extreme cases, your IP address or domain might end up on blacklists.
Warm up your server
Don't start with a large volume. It's better to gradually increase sending and build algorithm trust.
Clean your database
The fewer invalid addresses and hard bounces, the lower the risk of reputation issues.
Monitor results
Observe bounces, responses, server errors, and signs that deliverability is declining.
✓ Summary — cold mailing is a process, not a magic button
Sending cold emails is not a trip to Mars, but it's also not just clicking "Send" in Gmail to a thousand people at once. It's a logical process: server, domain, DNS, pace, database, testing, and reputation control.
If you take care of these elements, you increase the chances that your messages will appear professional to email systems and reach where they should.
Ready to act, but missing contacts?
Check out our tools and databases for B2B activities. You can use B2B Machine, a company database, an email marketing database, or commission a campaign if you want to move faster from planning to actual sending.
Want to commission a campaign or set up your own infrastructure? Write to us—we'll advise you on where to start.