The connection
Whether the host and port answer at all, and whether the encryption setting matches what they expect. A wrong port or the wrong encryption mode usually fails here, before any credential is offered.
SMTP Tester
Test your SMTP server configuration and send a test email.
Privacy Note
Your SMTP credentials are used only for this test and are not saved on our servers.
What it checks
Three Separate Things That All Look Like One Failure
An smtp test tool is worth having because when mail will not send, the useful question is which of three stages refused you. The error text tells you, and this page is mostly a way of getting to that error quickly.
The login
Whether the username and password are accepted. This is the stage that fails when a provider wants an app-specific password rather than the account password, which is a common and confusing case.
The send
Whether the server will actually relay a message from the address you gave. A login can succeed and the send still be refused, usually because the from-address is not one the account is allowed to send as.
Why on a marketplace
A Quarter of the Email Shelf Is Sold on Protocol Access
This is not a general utility that wandered onto the site. It answers the question the catalogue creates.
The listing promises a protocol, not an inbox
Of the live email listings here, more than a thousand name IMAP, SMTP or POP3 somewhere in the title or the description. That is a claim about how you will reach the mailbox, and it is exactly the kind of claim that is cheap to write and easy to get wrong.
The window to complain is short
Warranty on this site starts when the order is delivered, not when you get around to testing it, and on most listings it is measured in hours. Testing on arrival is not diligence, it is the only moment the test is worth anything.
Reading the result
What a Pass and a Fail Each Prove
A test result is narrower than it feels. Both outcomes are worth having and neither means what people usually take it to mean.
| What it proves | What it does not | |
|---|---|---|
| It sent | The host answered, the credentials were accepted, and the server relayed a message from that address, at that moment. | That it will work tomorrow, that the mailbox is not shared, or that nobody else holds the same password. |
| Login refused | Something about the username, the password or the authentication method is wrong. | That the credentials are fake. Providers often require an app-specific password, and the account password will fail cleanly against a perfectly real mailbox. |
| Connection refused | The host, the port or the encryption setting does not match. This is a configuration answer, not a credential one. | That the account is bad. You have not reached the point of offering a credential yet. |
A passing test is a snapshot, not a warranty. It tells you the credentials worked once. It cannot tell you how many copies of those credentials exist, and on a bought mailbox that is the question that decides whether it is still yours next week. Change the password once you are in.
Before you test
The Five Fields, and Which One Usually Is the Problem
To test smtp server access you need five things, and four of them are copied from a listing without much thought. The fifth is where most failures live.
Host and port
These travel together and a mismatched pair is the commonest cause of a failed smtp connection test. A provider usually publishes more than one port, each expecting a different encryption mode, and picking the wrong combination fails before any credential is offered.
Encryption
Implicit or explicit, and the port decides which. This is the field people leave at whatever the form defaulted to, and it is the reason a set of perfectly good mailbox credentials appears to be rejected.
Username and password
Where smtp authentication actually happens, and where an app-specific password is often required instead of the account password. If the listing gave you one and not the other, that gap is the finding rather than the credential being fake.
The from address
You cannot send test email as an address the account is not permitted to send as. A login can succeed and the send still be refused for this reason alone, which reads as a credential failure and is not one.
Limits
What This Page Will Not Do
Said plainly, because the useful part of a diagnostic is knowing where it stops.
It does not read your mail
Sending and receiving are different protocols. This checks the sending side. If you need to know whether mail arrives, that is IMAP or POP3 and a different check.
It cannot tell you why a provider blocked you
A server can accept a login and still silently drop or quarantine what you send, for reasons it does not disclose. A successful test proves the door opened, not that anything walked through it.