ToolSci.com

📤 SMTP Tester

Check if an SMTP mail server is reachable and accepting connections.

ℹ️ About SMTP Tester

The SMTP Tester is a diagnostic tool for verifying the availability and responsiveness of outgoing mail servers. SMTP (Simple Mail Transfer Protocol) is the standard for email transmission, and if your server is unreachable or blocked, your applications and users will be unable to send mail.

This tool performs a low-level handshake with the specified server and port. It verifies that the server is listening and ready to accept commands by sending a NOOP request. This is particularly useful for troubleshooting firewall issues, verifying that your ISP is not blocking port 25, or confirming that a new mail relay has been correctly configured before you put it into production.

📖 How to use SMTP Tester

  1. 1. Enter the hostname or IP address of the SMTP server (e.g., <code>smtp.office365.com</code>).
  2. 2. Specify the port number (common ports are 25, 465, and 587).
  3. 3. Click 'Run Tool' to initiate the connectivity test.
  4. 4. Review the status message to confirm if the connection was successful.

❓ Frequently Asked Questions

Which port should I use?

Port 587 is the standard for modern encrypted submission. Port 465 is used for SMTPS (SSL), and Port 25 is the traditional port for server-to-server relay (often blocked by residential ISPs).

Does this tool send a real email?

No. It only establishes a connection and sends a 'No Operation' command. It does not attempt to authenticate or transmit any message data.

What does a timeout error mean?

A timeout usually means that a firewall or network security group is blocking the connection, or the server address is incorrect.

🔗 Related Email Tools

📧

Email Validator

Verify the format and domain mail servers (MX) of an email address.
📬

MX Record Lookup

Find the Mail Exchange (MX) records for a domain.
🛡️

SPF Record Checker

Check if a domain has a valid Sender Policy Framework (SPF) record.
🔑

DKIM Checker

Verify a domain's DomainKeys Identified Mail (DKIM) record using a selector.
📋

DMARC Checker

Lookup a domain's Domain-based Message Authentication, Reporting, and Conformance (DMARC) record.
🔬

Email Header Analyzer

Paste raw email headers to analyze the sender, route, and authentication details.