Why your email validation with Regex is probably wrong
Hello everyone, I want to talk about a subject that seems simple but hides a lot of complexity: email address validation. If you work in development, you have most likely resorted to a regular expression found online to validate an email field. Copying and pasting a Regex from Stack Overflow is common, but in practice that solution often fails against many real cases and what official technical standards dictate.
The RFCs that define email syntax allow formats and exceptions that 99 percent of common regular expressions do not cover. That is why the only 100 percent safe way to know if an address exists and receives messages is to send it an email and verify the response or user confirmation. In registration flows, this is resolved with a confirmation link or a code, simple and effective.
However, when you manage a historical database with thousands of addresses collected over time, you cannot send a verification email to every row without taking risks. Mass campaigns against dirty lists produce high bounce rates, spam complaints, and damage to the reputation of the domain and sending IPs. Buying email lists is also not worth it, a practice that should always be avoided.
If we cannot trust Regex and it is not feasible to verify each address by sending a message, what can be done to clean a contact database? A practical strategy is to validate the two parts of the email separately: the local part before the at sign and the domain after the at sign. With that separation, we can filter out many errors without sending unnecessary mass emails.
Domain validation through DNS queries is the first and most important check. A simple DNS verification provides a lot of information about a domain's ability to receive emails. Check if the domain exists by querying its NS name servers. If there are no NS records, it is very likely that the domain is not registered or is not configured correctly.
The MX record is key because it indicates which servers accept mail for that domain. If there are no MX records, it is very likely that the domain does not reliably receive email. For greater security, it is also advisable to resolve the A or AAAA records of the servers listed in the MX and verify that they point to active IPs.
In addition to the existence of the domain and MX records, you must watch out for temporary or disposable email services. Platforms like Temp Mail or 10 Minute Mail generate addresses that expire in minutes or hours. Sending campaigns to those domains wastes resources and deteriorates engagement metrics. There are lists maintained in public repositories that contain disposable domains, and it is advisable to compare them against your database to remove that noise.
Another important topic is functional or role-based addresses like sales at, support at, or contact at. These are emails shared by teams or functions, and the person responsible who receives a message may consider it unsolicited and mark it as spam. For commercial sends, it is advisable to segment or exclude these contacts depending on the type of campaign.
Keep in mind that although these checks greatly improve list quality, they do not guarantee that the user's account exists or that the local part is well written. What they do achieve is dramatically increasing the probability that an address is correctly structured and points to a legitimate domain capable of receiving email, reducing bounces from non-existent domains, detecting disposable addresses, and allowing functional addresses to be treated differently.
At Q2BSTUDIO, as a custom software and application development company, we offer integrated solutions for list hygiene and email validation, combining DNS verification tools, disposable domain detection, and email confirmation strategies. We are specialists in custom software, artificial intelligence, cybersecurity, and aws and azure cloud services, so we can design validation flows that integrate with your systems and reduce risks in campaigns and messaging operations.
Our capabilities in business intelligence and artificial intelligence services allow us to automate cleaning rules and enrich data for more precise segmentation. If your company is looking for AI for businesses or AI agents to automate verification and support tasks, Q2BSTUDIO develops customized solutions that include Power BI dashboards to monitor list health and key metrics.
We implement secure and scalable architectures, applying cybersecurity practices at every point of the process, and we leverage aws and azure cloud services to ensure availability and performance. Additionally, we can integrate real-time verification APIs into your forms and registration processes, preventing the accumulation of invalid addresses from the first contact.
If you want to improve the deliverability and reputation of your sends, we recommend combining at least these actions: DNS validation of domains, checking against disposable email lists, detection of functional addresses, and verification by confirmation when possible. All of this can be orchestrated through custom software solutions that Q2BSTUDIO develops for different sectors.
How we do it in practice depends on your priorities and data volume. We can offer an initial evaluation of your list, cleaning proposals, and automation with AI agents that reduce manual work and improve conversions. If you are interested in optimizing processes with artificial intelligence, AI agents, and business intelligence tools like Power BI, contact our team to design a custom solution. At Q2BSTUDIO, we transform needs into secure and efficient custom applications and custom software.
And you, how do you validate emails in your company, and which tools have worked best for you to maintain the hygiene of your lists?
