In 2019 I tested the deliverability of several email tools and watched how they behaved in different inboxes. It was useful experience, not a lifelong ranking of winners. Providers, filters and rules change. What does not change is the sender's responsibility for technology, database quality and content.
When a campaign fails, people often change the button colour or the tool. The problem is usually one floor below: the message went to spam, the recipient does not remember signing up, the segment is too broad or the next step makes no sense.
Four layers that must hold together
- Law and expectations: you know why you may write to the person and what they expected when signing up.
- Technical credibility: the domain is verified, transmission is secure and sending can be traced.
- Database quality: contacts are current, segmented and easy to unsubscribe from.
- Relevant content: the message addresses a specific situation and leads to a sensible next step.
If one layer is missing, the others will not save it in the long term.
Technical minimum for deliverability
Send from your own domain and set up SPF or DKIM; for regular sending I recommend both. DMARC tells recipients how to handle messages that fail authentication and gives you reports. Coordinate records with every service sending on behalf of the domain. Two separate SPF records are not double protection.
In its current sender requirements for Gmail, Google lists at least SPF or DKIM, valid forward and reverse DNS, TLS and a low spam-complaint rate for all senders. Senders of more than 5 000 messages a day to personal Gmail accounts need SPF, DKIM, DMARC, domain alignment and, for marketing messages, one-click unsubscribe together with a visible link in the body. Smaller senders also benefit from approaching these standards.
Monitor rejected messages, temporary errors, complaints and domain reputation. A shared IP is not automatically bad, and a dedicated IP is not automatically better. Your own infrastructure requires sufficient stable volume, warming and operational oversight.
A database is not a warehouse of addresses
For every contact you should be able to find the source, date, expected communication scope and any consent or customer relationship. The official Czech DPA FAQ summarises Czech commercial-communication rules and the customer exception. Do not turn a legal decision into an automatic yes/no field; a more detailed practical map is in the GDPR for online marketing article.
Double opt-in is not a magic legal phrase for every situation, but it is a very good way to verify an address and document registration. Regularly separate inactive and undeliverable contacts. Buying someone else's database is simultaneously an expectations, reputation and legal problem.
Segment by situation, not imagination
Start with a few groups that genuinely change the message:
- a new prospect and an existing client,
- the specific service or product they showed interest in,
- decision stage or last meaningful activity,
- language and country where these change the offering or legal regime.
Do not create thirty segments for which you have no different content. And do not collect sensitive inferences about a person merely because the form allows it.
Content without magic percentages
There is no universal rule that an email must contain an exact text-to-image ratio, three links or three kilobytes. Filters assess many signals, and recipients use different devices and settings. I follow a more practical foundation:
- the sender and subject match what the person expects,
- the main message is understandable without loaded images,
- links lead to safe, relevant pages,
- one primary next step is clear,
- the footer identifies the sender and makes unsubscribing easy,
- HTML also has a text alternative and is readable on mobile.
Write so it is clear why the message arrived right now. Personalising an irrelevant mailing with a first name does not create a relationship.
How to choose an email tool
I no longer repeat old tool rankings. Base the choice on your own scenario and verify it in a test campaign. In particular you need:
- domain verification and understandable deliverability reports,
- data export, consent history and simple handling of data-subject rights,
- segmentation and automation you will actually use,
- a reliable webhook or integration with your CRM and website,
- management of unsubscribes, suppression lists and user roles,
- contractual and security terms appropriate to your operation.
For orientation you can use my comparison of email tools, but make the final choice using current documentation and your own test.
Measurement that does not chase opens alone
Because of privacy protections and image loading, an open is an imprecise signal. For operations, monitor delivery, rejection, complaints, unsubscribes and clicks. For business, monitor qualified visits, replies, enquiries, orders and value over time.
Tag campaign links consistently with UTM parameters. In analytics, check that email does not credit conversions only to itself because it was the last click. The person may previously have arrived from search, a webinar or a referral.
A simple operating rhythm
- Before sending, test the sender, subject, links, mobile display, unsubscribe and measurement.
- After sending, check errors and complaints, not just the revenue graph.
- Once a month, review database growth, sources, activity and the suppression list.
- Once a quarter, verify DNS, roles, integrations, export and retention rules.
- Always test changes against a clear hypothesis and business result.
Email marketing makes no sense without responsibility for the database and regular content. If you send twice a year and have to rediscover the process each time, simplify it first. To review technology, data and automation as one whole, use the contact page.