SMTP configuration

SMTP connection settings the main process expects, plus provider-specific defaults and how the UI persists a sanitized config.

The SMTP functionality is implemented in the Electron main process and exposed to the renderer via IPC. The key components are:

• SMTP handler: creates transporters, verifies connections, sends emails, and manages progress events
• SMTP form: collects SMTP configuration and email content from the user
• Main process: registers IPC handlers and routes requests
• Preload bridge: exposes secure IPC methods to the renderer

graph TB
UI["SMTPForm.jsx<br/>Collects SMTP config and content"] --> IPC["preload.js<br/>IPC bridge"]
IPC --> Main["main.js<br/>Registers 'smtp-send' handler"]
Main --> Handler["smtp-handler.js<br/>handleSMTPSend()"]
Handler --> Nodemailer["nodemailer<br/>Transporter creation"]
Handler --> Store["electron-store<br/>Optional credential storage"]

• SMTP configuration fields supported by the UI:
• Host
• Port
• Username/Email
• Password
• Secure connection toggle (SSL/TLS)
• SMTP handler behavior:
• Validates presence of host, port, user, and pass
• Optionally saves host, port, secure, and user to encrypted storage
• Creates a Nodemailer transporter with host, port, secure, auth, and TLS options
• Verifies the connection before sending
• Sends emails sequentially with configurable delay between attempts
• Emits progress events for each recipient
• IPC exposure:
• Renderer invokes “smtp-send” via preload bridge
• Main process routes to handler
• Handler returns results and errors

The SMTP workflow spans UI input, IPC routing, and the main process handler.

sequenceDiagram
participant UI as "SMTPForm.jsx"
participant Bridge as "preload.js"
participant Main as "main.js"
participant Handler as "smtp-handler.js"
participant Transport as "Nodemailer Transporter"
participant Provider as "SMTP Server"
UI->>Bridge : "sendSMTPEmail(smtpData)"
Bridge->>Main : "ipcRenderer.invoke('smtp-send', smtpData)"
Main->>Handler : "handleSMTPSend(event, smtpData)"
Handler->>Transport : "createTransport({host,port,secure,auth,tls})"
Handler->>Transport : "verify()"
loop For each recipient
Handler->>Transport : "sendMail({from,to,subject,html,text})"
Transport-->>Handler : "result"
Handler->>UI : "email-progress (sending/sent/failed)"
end
Handler-->>Main : "{success,results}"
Main-->>Bridge : "{success,results}"
Bridge-->>UI : "{success,results}"

SMTP configuration parameters#

• Host: SMTP server hostname or IP address
• Port: Numeric port number
• Username/Email: Sender identity used for authentication
• Password: Credential for authentication
• Secure connection: Boolean flag controlling SSL/TLS behavior

These fields are collected in the SMTP form and passed to the handler.

Transporter creation and security options#

• Transporter options include host, port, secure, auth, and TLS
• The secure flag is used to select SSL/TLS mode
• TLS rejectUnauthorized is configured to accept self-signed certificates

flowchart TD
Start(["Create Transporter"]) --> HostPort["Set host and port"]
HostPort --> SecureFlag{"secure flag?"}
SecureFlag --> |true| SSL["Enable SSL/TLS"]
SecureFlag --> |false| NoSSL["Disable SSL/TLS"]
SSL --> Auth["Set auth (user, pass)"]
NoSSL --> Auth
Auth --> TLS["TLS options"]
TLS --> Verify["Verify connection"]
Verify --> End(["Ready to send"])

Connection verification and retry behavior#

• The handler performs a connection verification before sending
• There is no explicit retry mechanism in the handler; failures are reported per recipient
• The UI displays per-recipient status and error messages

sequenceDiagram
participant Handler as "smtp-handler.js"
participant Transport as "Nodemailer Transporter"
Handler->>Transport : "verify()"
alt Success
Transport-->>Handler : "OK"
Handler->>Handler : "Proceed to send"
else Failure
Transport-->>Handler : "Error"
Handler-->>Caller : "{success : false,error}"
end

Rate limiting and delays#

• The handler applies a configurable delay between sending each email
• Delay is passed in milliseconds and used to throttle requests

flowchart TD
Start(["Send next email"]) --> Delay["Wait delay ms"]
Delay --> Send["sendMail()"]
Send --> Next{"More recipients?"}
Next --> |Yes| Delay
Next --> |No| End(["Complete"])

Authentication methods#

• Username/password authentication is supported via the auth object
• OAuth2 is supported for Gmail via a separate handler
• API keys are not directly supported by the SMTP handler; use OAuth2 or username/password

Credential storage#

• The handler can optionally persist host, port, secure, and user to encrypted storage
• Password is not saved for security

Provider-Specific settings#

Provider-specific recommendations are documented in the project’s README. These include:

• Gmail SMTP: host, port, and security guidance
• Outlook SMTP: host, port, and security guidance

Use these values in the SMTP form fields.

The SMTP handler relies on external libraries and Electron modules.

graph TB
SMTPHandler["smtp-handler.js"] --> Nodemailer["nodemailer"]
SMTPHandler --> Store["electron-store"]
Main["main.js"] --> SMTPHandler
Preload["preload.js"] --> Main
Package["package.json"] --> Nodemailer
Package --> Store

• Sequential sending: Emails are sent one after another with a configurable delay
• No connection pooling: The handler creates a single transporter and reuses it for verification and sending
• Network timeouts: The handler does not set explicit timeouts; rely on underlying network defaults
• Rate limiting: Use the delay setting to avoid throttling or rate limits

Common SMTP issues and checks derived from the codebase:

• Incomplete configuration: Ensure host, port, user, and pass are provided
• Connection verification failure: The handler validates connectivity before sending
• Self-signed certificates: TLS rejectUnauthorized is set to accept self-signed certs
• Per-recipient failures: Errors are emitted per recipient via progress events

Operational tips:

• Verify server settings and firewall rules
• Confirm correct port and security mode
• Use appropriate delays to avoid rate limits

Verify the transport before a bulk run. Most provider failures are wrong port/TLS pairing or an app-password requirement you skipped.

Configuration templates#

Use these templates to quickly set up SMTP for common providers. Fill in the host, port, username/email, and password fields in the SMTP form.

• Gmail SMTP

• Host: smtp.gmail.com

• Port: 587 (TLS) or 465 (SSL)

• Security: Enable secure connection (SSL/TLS)

• Authentication: Use App Password (not regular password)

• Outlook SMTP

• Host: smtp-mail.outlook.com

• Port: 587

• Security: TLS

• Authentication: Username/password

Security considerations#

• Credential encryption: The handler can persist host, port, secure, and user to encrypted storage; password is not saved
• Certificate validation: TLS rejectUnauthorized is set to accept self-signed certificates
• Secure connection establishment: Use the secure connection toggle to enable SSL/TLS as required by your provider