Email Server Test
Check MX records and SMTP connectivity for any domain in seconds. Diagnose mail server issues before you send.
Understanding Email Server Tests
Before sending email to a domain, it is worth confirming that the domain has a mail server configured to receive messages. A missing or misconfigured MX record means any email sent to that domain will bounce immediately — a hard bounce that damages your sender reputation with ESPs like Google and Microsoft.
This tool performs two checks: a DNS MX lookup to find the mail servers responsible for the domain, and a direct TCP connection attempt to port 25 of the primary MX server to verify it is actively accepting SMTP connections.
What Are MX Records?
MX (Mail Exchange) records are DNS entries that tell the internet which server handles incoming email for a domain. When someone sends a message to [email protected], the sending server queries DNS for acme.com's MX records, then connects to the server listed there. Multiple MX records can exist with different priority values — lower numbers indicate higher priority, providing redundancy if the primary server is unavailable.
Common MX providers include Google Workspace (aspmx.l.google.com), Microsoft 365 (mail.protection.outlook.com), and Proofpoint. The MX record alone does not confirm a specific mailbox exists — that requires SMTP verification at the user level, which FareOf provides.
When Port 25 Is Blocked
A non-responsive port 25 does not necessarily mean the mail server is broken. Many cloud hosting providers and ISPs block outbound connections on port 25 to prevent spam. Large providers like Google and Microsoft often filter unauthenticated port 25 probes from unknown IPs. In practice, their servers are receiving mail fine — they simply restrict who can connect on that port at the protocol level.
For deliverability testing and email verification, FareOf uses dedicated SMTP verification infrastructure with established IP reputation specifically to perform these checks at scale and accurately.
Frequently Asked Questions
What does an email server test check?
It looks up MX DNS records for the domain and probes whether the primary mail server responds on port 25 — the standard SMTP reception port.
Why might a mail server not respond on port 25?
Many hosting providers block outbound port 25 to prevent spam. The server may also firewall connections from unknown IPs while still accepting legitimate delivery.
What is an MX record?
A DNS entry specifying which mail server handles incoming email for a domain. Multiple records with priority values provide redundancy.
What does the SMTP banner tell me?
The greeting message sent when a connection is established — typically includes the mail server software name and can hint at the infrastructure in use.
Need full email verification?
FareOf goes beyond server tests — we verify individual mailboxes exist using real SMTP probes across triple-redundant infrastructure with established IP reputation.
Try Free Email Finder