Test Email Address in VB, ASP, C++, Delphi - SMTP Component

TestEmailAddr Method

Validate if recipient's email address is valid or accepted by specified SMTP server.

[Syntax] Visual C++: HRESULT TestEmailAddr(long* pVal) Visual Basic: TestEmailAddr() As Long

Return Value

If this method succeeds, the return value is zero; otherwise the return value is non-zero.

Remarks

With this method, your application can test if an email address is valid. Warning: it is not 100% correct.

How does it work? Firstly, Mail object performs a DNS MX record query. If it queries the recipient's local SMTP server successfully, Mail object will try to connect to this server. Mail object then performs "RCPT TO" command to test if this SMTP server accepts this email address. If you specified a SMTP server, then this method tests if the specified SMTP server accepts this email address.

Before invoking this method, please make sure your computer is connected to the Internet.

Example

[VB6, VBA - Test Email Address] Private Sub TestEmailAddress() Dim oSMTP As New EASendMailObjLib.Mail oSmtp.LicenseCode = "TryIt" oSmtp.FromAddr = "sender@mydomain.com" 'validate the following email address oSmtp.AddRecipient "tester", "tester@mydomain.com" If oSmtp.TestEmailAddr() = 0 Then MsgBox "valid email address" Else MsgBox "it may be an invalid email address" MsgBox oSmtp.GetLastErrDescription() End If End Sub

Test Email Address

Example for Testing Email Address

Validate Email Address Syntax and Test Email Address in VB6
Validate Email Address Syntax and Test Email Address in VC++
Validate Email Address Syntax and Test Email Address in Delphi

How does it work?

Firstly, Mail object performs a DNS MX record query. If it retrieves the recipient's local SMTP server successfully, Mail object will try to connect to this server. Mail object then performs "RCPT TO" command to test if this SMTP server accepts this email address.

Why we don't recommend testing email address?

Because it totally depends on your networking connection, if your networking connection to the recipient server is bad or your IP address is blocked by the recipient server, test will be failed, but it doesn't mean this email address is invalid.

Moreover, to prevent email address testing, many email providers accept the recipient address at first no matter if the address is valid or invalid, only after you sent the email data to the server, then the server rejects it if the recipient address is invalid.

Recommended Solution

Send the email to the recipient without testing. If you don't get Transport Error and Failure Report in 24 hours, that means the recipient is valid. If you get Failure Report, you should consider to remove this recipient from your mail listing.

See Also