C# email tutorial for SMTP sending and inbox testing

C# email workflows usually need two capabilities:

• send reliably through SMTP or API,
• verify receive behavior in tests.

This guide covers both using MailKit and MailSlurp.

Architecture in one view

Recommended libraries for C# email

Use:

• for robust SMTP and MIME handling.
• NuGet package for disposable inboxes, waits, and verification helpers.

Install packages:

Configure MailSlurp in .NET

Imports:

Set your API key and configuration:

Create a disposable inbox for testing:

Send email with MailKit

Build a :

Send with configured SMTP client:

Receive and assert email in tests

Wait for the message using :

Fetch by ID when needed:

Attachment handling

Use for multipart content and attachments:

Then send with the same SMTP client workflow.

Validate addresses before send

To reduce bounce risk, validate addresses before large sends:

Multiple recipients

Example test pattern: verification emails

Use a browser test (Selenium/Playwright), then assert email delivery:

Extract a verification code:

Production checklist for C# email

• Configure SMTP TLS and timeout values explicitly.
• Track send failures by SMTP response class.
• Keep inboxes isolated per test run in CI.
• Assert subject/body/token behavior before release.

Next resources

• CSharp MailSlurp documentation
• Test emails with Selenium and CSharp
• Disposable email accounts for .NET