OrchardCMS/OrchardCore · error · ArgumentException

The type must implement the 'IEmailProvider' interface.

Error message

The type must implement the 'IEmailProvider' interface.

What it means

EmailProviderTypeOptions wraps a provider implementation Type and validates at construction that the type implements IEmailProvider. Passing any other type is rejected immediately with this ArgumentException, keeping provider registration type-safe.

Solutions

1. Make the registered type implement IEmailProvider (and IAsyncDisposable if needed)
2. Fix the type reference in the options setup so it points at the intended provider class
3. Add a startup-time assertion/test that all configured provider types implement IEmailProvider

Example fix

// before
services.Configure<EmailProviderOptions>(o => o.Providers["smtp"] = new EmailProviderTypeOptions(typeof(SmtpService)));
// after
public sealed class SmtpEmailProvider : IEmailProvider { ... }
services.Configure<EmailProviderOptions>(o => o.Providers["smtp"] = new EmailProviderTypeOptions(typeof(SmtpEmailProvider)));

if (!typeof(IEmailProvider).IsAssignableFrom(providerType))
    throw new ArgumentException($"{providerType} must implement IEmailProvider before registration");

bool IsValidProviderType(Type t) => t is not null && typeof(IEmailProvider).IsAssignableFrom(t);

try { options.Providers[name] = new EmailProviderTypeOptions(type); } catch (ArgumentException ex) { _logger.LogCritical(ex, "Bad email provider registration for {Name}", name); throw; }

When it happens

Trigger: Registering an email provider with `new EmailProviderTypeOptions(typeof(SomeService))` where SomeService does not implement IEmailProvider; configuring EmailProviderOptions.Providers dictionary with a wrong or renamed type.

Common situations: Typo or wrong type passed during AddEmailProvider/options configuration; a custom provider class refactored away from IEmailProvider but still referenced in options setup; DI startup code copied from another module without updating the type.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• ' ' is an invalid Email provider name.
• The SMTP pickup directory location is invalid.
• A feature is missing a mandatory 'Id' property in the Module
• Could not resolve extension for type
• Could not resolve main feature for type

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/7a107a4aee3f03e4. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore/OrchardCore.Email.Core/Services/EmailProviderTypeOptions.cs:11

namespace OrchardCore.Email.Services;

public class EmailProviderTypeOptions
{
    public Type Type { get; }

    public EmailProviderTypeOptions(Type type)
    {
        if (!typeof(IEmailProvider).IsAssignableFrom(type))
        {
            throw new ArgumentException($"The type must implement the '{nameof(IEmailProvider)}' interface.");
        }

        Type = type;
    }

    public bool IsEnabled { get; set; }
}

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