EmailVerify.NET

EmailVerify.NET can check if an email address exists without sending email messages; it does so by emulating the behavior of common mail exchangers and employing the SMTP protocol wisely, while respecting the Netiquette rules to avoid the originating IP address being tagged as a potential source of spam. Due to the nature of this check, the validation process may be affected by multiple factors, including network latency and configuration; EmailVerify.NET keeps track of the eventual errors as well as the possible temporarily failures and report them back for further analysis.

The following code, for example, checks if a given email address exists and, in case of failure, follows different execution paths based on the exact cause of the error, as determined by the component:

            var verifier = new EmailVerifier();

            // ...

            var result = verifier.Verify("bob@example.com",
                VerificationLevel.Mailbox);

            if (result.IsSuccess)
            {
                // The mailbox exists
            }
            else
            {
                switch (result.Status)
                {
                    case VerificationStatus.LocalSenderAddressRejected:
                        // The foreign mail exchanger rejected our sender address
                        break;

                    case VerificationStatus.MailboxConnectionFailure:
                        // A network failure happened while connecting to the foreign
                        // mail exchanger
                        break;
                    
                    case VerificationStatus.MailboxDoesNotExist:
                        // The mailbox does not exist
                        break;

                    case VerificationStatus.MailboxTemporarilyUnavailable:
                        // The mailbox is temporarily unavailable: we need to validate
                        // it again in a few minutes (greylisting)
                        break;

                    case VerificationStatus.MailboxValidationTimeout:
                        // A timeout occured while validating the mailbox; we need
                        // to increase the related settings value
                        break;

                    case VerificationStatus.ServerDoesNotSupportInternationalMailboxes:
                        // The local part of the address is in a non-ASCII encoding but
                        // the foreign mail exchanger can't handle this type of addresses
                        break;

                    // TODO: Add more cases, if needed

                    default:
                        // ...
                        break;
                }
            }