MailkitSender Implementation

# MailkitSender Implementation

Overview

MailkitSender is an email sender that mirrors SmtpSender functionality but adds proxy support via MailKit's ProxyClient. It implements the IEmailSender interface and uses MailKit.Net.Smtp.SmtpClient instead of System.Net.Mail.SmtpClient.

When MailkitSender is Used

The sender selection logic (in EmailTemplateService.cs and GiftboxService.cs) checks whether an EmailProfileAddress has an active proxy configured:

• If the sender type is "smtp", "outlook", "gmailapi", or "hmail" AND an active EmailProfileAddressProxy record exists linking it to an active ProxySettings → MailkitSender is used.
• Otherwise → SmtpSender is used (unchanged behavior).

New Entities

ProxySettings

Property	Type	Description
Id	int	Primary key
Name	string	Display label (max 255)
Host	string	Proxy server hostname/IP (required, max 255)
Port	int	Proxy server port (required)
Username	string	Optional proxy auth username (max 255)
Password	string	Optional proxy auth password (max 255)
ProxyType	string	"Socks5" or "HttpConnect" (max 50)
Active	bool	Whether this proxy is enabled

EmailProfileAddressProxy

Property	Type	Description
Id	int	Primary key
EmailProfileAddressId	int	FK → EmailProfileAddresses
ProxySettingsId	int	FK → ProxySettings
Active	bool	Whether this proxy link is active

Architecture

EmailProfileAddresses (existing)
        │
        │ 1:N via EmailProfileAddressProxy
        ▼
EmailProfileAddressProxy (junction table)
        │
        │ N:1
        ▼
ProxySettings (reusable proxy definitions)

A single ProxySettings record can be shared across multiple email profile addresses.

Proxy Types Supported

ProxyType	MailKit Class	Use Case
Socks5	Socks5Client	SOCKS5 proxy (common for tunnels)
HttpConnect	HttpProxyClient	HTTP CONNECT proxy

SSL/TLS Handling

MailKit uses SecureSocketOptions instead of EnableSsl:

Port	SecureSocketOptions
465	SslOnConnect
587	StartTls
Other	Auto

Internal servers (mail.soproserver.co.uk, 185.22.252.171) use SecureSocketOptions.None.

Key Differences from SmtpSender

Aspect	SmtpSender	MailkitSender
SMTP Client	System.Net.Mail.SmtpClient	MailKit.Net.Smtp.SmtpClient
Proxy Support	None	SOCKS5 / HTTP CONNECT via ProxyClient
Message Format	MailMessage → send directly	MailMessage → MimeMessage → send
SSL Config	EnableSsl = true	SecureSocketOptions enum
Send Method	Synchronous client.Send()	Async client.SendAsync()
Constructor	Parameterless or with log svc	Requires ProxySettings

Files Changed/Created

File	Action
SoProEntities/SoProEntities/ProxySettings.cs	Created
SoProEntities/SoProEntities/EmailProfileAddressProxy.cs	Created
Services/Services/Email/MailkitSender.cs	Created
SoproData/SoproData/SoProDataContext.cs	Added DbSets
Services/Services/EmailTemplateService.cs	Modified sender selection
Services/Services/GiftBox/GiftboxService.cs	Modified sender selection
Services/Services/Services.csproj	Updated package refs + added file
Services/Services/packages.config	Updated package versions
SoProEntities/SoProEntities/SoProEntities.csproj	Added new entity files

Database Migration Required

After deploying, run EF migrations or manually create tables:

CREATE TABLE ProxySettings (
    Id INT IDENTITY(1,1) PRIMARY KEY,
    Name NVARCHAR(255) NOT NULL,
    Host NVARCHAR(255) NOT NULL,
    Port INT NOT NULL,
    Username NVARCHAR(255) NULL,
    Password NVARCHAR(255) NULL,
    ProxyType NVARCHAR(50) NOT NULL,
    Active BIT NOT NULL DEFAULT 1
);

CREATE TABLE EmailProfileAddressProxy (
    Id INT IDENTITY(1,1) PRIMARY KEY,
    EmailProfileAddressId INT NOT NULL,
    ProxySettingsId INT NOT NULL,
    Active BIT NOT NULL DEFAULT 1,
    CONSTRAINT FK_EmailProfileAddressProxy_EmailProfileAddresses 
        FOREIGN KEY (EmailProfileAddressId) REFERENCES EmailProfileAddresses(Id),
    CONSTRAINT FK_EmailProfileAddressProxy_ProxySettings 
        FOREIGN KEY (ProxySettingsId) REFERENCES ProxySettings(Id)
);

Usage Example

To route an email profile address through a proxy:

1. Create a ProxySettings record with proxy host/port/credentials.
2. Create an EmailProfileAddressProxy linking the EmailProfileAddresses.Id to the ProxySettings.Id with Active = true.
3. The sender selection logic will automatically pick MailkitSender for that address.