Jak wysłać skuteczny mailing (i nie trafić do SPAMu)? Poradnik krok po kroku

How to send effective emails (and avoid SPAM)? A step-by-step guide

Hi! If you've landed here, you probably already have a great email address database, a brilliant idea for an email, and you're wondering... what's next? How do you technically send it so it doesn't end up in the SPAM folder of a potential client?

Many beginners think that all they need to do is dump a thousand addresses into the BCC field of their Gmail and click "Send". Spoiler: that's the fastest way to get your account blocked and burn your domain. Real cold mailing requires a bit of preparation, but don't worry – you don't need to be a Silicon Valley programmer to figure it out.

I've prepared a simple, friendly guide for you. I'll tell you how we do it, using the simplest (and cheapest!) solutions. Ready? Let's go!

Table of Contents (Click to jump to section):

  1. VPS Server and Port 25 – How to choose a machine for sending?

  2. Sending script – how to space out email queues over time?

  3. The Holy Trinity: SPF, DKIM, and DMARC (It's simpler than you think)

  4. rDNS Record (PTR) – Your server's invisible business card

  5. Anti-spam tests – why Mail-Tester is your best friend

  6. Blacklists and IP reputation – avoid them at all costs

1. VPS Server and Port 25 – How to choose a machine for sending?

Let's start with the basics. You won't run a professional campaign from a regular hosting plan that costs 50 PLN a year, which you use for your cat blog. You need your own machine. In the IT world, this is called a VPS Server (Virtual Private Server). It sounds intimidating, but it's simply your private piece of a computer somewhere in the cloud, working just for you 24/7.

Choosing the right VPS is a matter of life and death for your campaign. Not every machine is suitable for this. A good server for mailing must meet four ironclad rules:

  • Clean IP: Your server gets a unique IP address on the network. If you buy the cheapest server, you might get a "recycled" IP that someone previously used to send SPAM, Viagra, and scams. With such an address, your email database will immediately end up in the trash. You must ensure that the IP is crystal clear.

  • Open Port 25: This is the port through which servers communicate and relay emails (known as SMTP traffic). Most cheap hosting companies block it by default and won't unblock it.

  • Ability to set an rDNS record: A professional provider allows full editing of the so-called reverse DNS (more on this in point 4!).

  • Provider's policy allowing mailing: Many providers have absurd clauses in their terms and conditions, which cause them to block servers after the first major sending – even if you are conducting a 100% legal, compliant B2B cold mailing. Your provider must be "Mailing-Friendly".

👉 Don't have time for searching and configuration? We have a ready solution. Do you need a clean VPS server with Debian 13 installed, perfectly suited for mailing campaigns and meeting all these rigorous guidelines? We have prepared a second, dedicated server (ready to handle small and medium-sized campaigns) that you can purchase directly from us.

2. Sending script – how to space out email queues over time?

You've got your server and a fresh B2B company database. What now? You can't send a thousand emails in one second. When Google or Microsoft see such a sudden burst, they immediately know it's an automated shot and block it as SPAM. The golden rule is: act like a human.

To make your sending look natural, you need a script that will take your email database and drip-feed messages. You could buy comprehensive sending tools that cost hundreds of dollars a month, but... why? We went for the path of least resistance.

We created our own, ultra-simple PHP script. It works straightforwardly: you upload it to the server, run it in a browser window, and set it to refresh. With each refresh, the script sends, for example, 5 emails and then pauses. Brilliant in its simplicity and ideal if your email database contains anywhere from a few hundred to several thousand contacts.

🎁 A gift from us: The script is not normally for sale, but if you buy any package from us (e.g., verified company databases in Poland), you'll receive this script as a gift for a grand total of 0 PLN! Just upload it to your server and you're good to go. Leave the tab open in your browser, and the emails will slowly but surely fly out to your clients.

 

3. The Holy Trinity: SPF, DKIM, and DMARC (It's simpler than you think)

If you want anyone to take you seriously (especially Gmail), your domain must have a digital ID. Without it, even the best company databases won't help – you'll hit a wall.

Imagine you're sending a letter.

  • SPF is a stamp on the envelope saying: "This server is authorized to send letters on my behalf".

  • DKIM is an invisible wax seal with your crest, guaranteeing that no one has tampered with the letter's contents en route.

  • DMARC is an instruction for the postman: "If the letter doesn't have my stamp and seal – throw it in the trash".

Configuring this means adding three lines of text (known as TXT records) in your domain's panel (where you purchased it). It takes literally 5 minutes and guarantees that anti-spam filters will give you the green light.

 

4. rDNS Record (PTR) – Your server's invisible business card

Have you configured SPF, DKIM, and DMARC? Great! But there's one more, extremely important detail that many people overlook – the rDNS record, commonly known as "reverse DNS" or PTR record. Imagine you're knocking on a client's door and introducing yourself as John Smith from Company X. A regular DNS system translates your domain name into an IP address (like checking a phone book for John Smith's number). Conversely, rDNS (Reverse DNS) works in reverse – the recipient's system takes your IP address and checks if entering it actually displays the domain from which you supposedly sent the email. This is a double credibility test, preventing impersonation.

Why is this so important? Because major players like Gmail, Outlook, and Yahoo immediately reject or mark as SPAM messages coming from servers that do not have a properly configured rDNS record. If they query your server's IP address and receive some strange string of characters from your hosting provider instead of the beautiful name of your domain (e.g., mail.yourdomain.com) in response, they will immediately consider you suspicious. This is an absolute technical foundation without which you should not even start sending.

How do you set it up? And here's the catch! Unlike SPF or DKIM records, the rDNS record is usually not set in the domain panel, but in the VPS server panel. Some providers offer a special text field in their client panel called "Reverse DNS" (where you simply enter your domain). Very often, however, there is no button there – you then need to write a short email (ticket) to your provider's technical support (Support) with a request: "Good day, please set the rDNS (PTR) record for my server with IP address [Your IP] to the value: mail.yourdomain.com". It takes a moment, but it is absolutely crucial for the success of your campaign.

 

5. Anti-spam tests – Mail-Tester is your friend

Before you send anything to your valuable clients (especially if it's a curated database of manufacturing companies or another niche), you MUST test your settings. Never shoot blind!

We use the free tool Mail-Tester.com. You go to their website, copy the generated temporary email address, and send your campaign to it. After a moment, you'll receive a brutally honest report evaluating your email on a scale of 0 to 10.

If the score is lower than 9/10 – do not send the campaign! Fix the errors. Below is a little proof from our side – this is what a correctly configured server by us looks like. Yes, that's a perfect 10/10. It's achievable!

 

6. Blacklists and IP reputation – avoid them at all costs

Finally, the most important thing. Even if you have perfectly cleaned company databases in Poland and a perfect server, everything can fall apart due to one detail: reputation.

Both your IP address (of the server) and your domain have their "credit history" with email providers. If your emails are frequently marked as SPAM by people, or if you send messages to non-existent addresses (known as hard bounces), you will end up on Blacklists. This is like an internet prison yard. Once you're there, none of your emails will reach the inbox.

How to defend against this?

  1. Warm up your server! Don't send 1000 emails on the first day. Start with 20, then 40 on the second day, 60 on the third... Build algorithmic trust.

  2. Maintain database quality. Sending emails to so-called spamtraps (spammer traps) will end your campaign. That's why, before we provide you with any company databases, we put them through proprietary scripts that verify email validity. With us, you only pay for contacts that actually work.

In summary – sending cold emails is not rocket science. It's a logical process. If you follow these steps, your emails will land directly on the desks of CEOs and managers. I'm rooting for your campaigns!

Ready for action, but lacking contacts? Check out our updated and ready-to-send

 

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