diff --git a/app/package-lock.json b/app/package-lock.json
index d94c363..8238cd0 100644
--- a/app/package-lock.json
+++ b/app/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@weaponsforge/sendemail",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@weaponsforge/sendemail",
-      "version": "2.0.0",
+      "version": "2.0.1",
       "license": "MIT",
       "dependencies": {
         "commander": "^14.0.3",
diff --git a/app/package.json b/app/package.json
index f1a5cca..9dba357 100644
--- a/app/package.json
+++ b/app/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@weaponsforge/sendemail",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "description": "Sends emails using Gmail SMTP with username/pw or Google OAuth2",
   "main": "dist/index.js",
   "types": "./dist/index.d.ts",
diff --git a/app/src/__tests__/build.test.ts b/app/src/__tests__/build.test.ts
new file mode 100644
index 0000000..6815969
--- /dev/null
+++ b/app/src/__tests__/build.test.ts
@@ -0,0 +1,83 @@
+import path from 'path'
+import { beforeAll, describe, expect, it } from 'vitest'
+
+import { buildHtml } from '@/lib/email/build.js'
+import { directory } from '@/utils/helpers.js'
+import { EmailSchemaMessages } from '@/types/email.schema.js'
+
+// buildHtml resolves the EJS template relative to __dirname (set to the build.ts location)
+beforeAll(() => {
+  globalThis.__dirname = path.resolve(directory(import.meta.url), '..', 'lib', 'email')
+})
+
+const TEST_RECIPIENTS = ['tester@gmail.com']
+const TEST_SENDER = 'sender@gmail.com'
+
+describe('buildHtml test', () => {
+  it('should return an HTML string from paragraph content', async () => {
+    const html = await buildHtml({
+      content: ['Hello, World!', 'Second paragraph'],
+      recipients: TEST_RECIPIENTS,
+      sender: TEST_SENDER,
+    })
+
+    expect(typeof html).toBe('string')
+    expect(html.length).toBeGreaterThan(0)
+  })
+
+  it('should return an HTML string from wysiwyg content', async () => {
+    const html = await buildHtml({
+      content: [],
+      recipients: TEST_RECIPIENTS,
+      sender: TEST_SENDER,
+      wysiwyg: '<p>Hello, wysiwyg!</p>',
+    })
+
+    expect(typeof html).toBe('string')
+    expect(html).toContain('Hello, wysiwyg!')
+  })
+
+  it('should strip script tags from wysiwyg content', async () => {
+    const html = await buildHtml({
+      content: [],
+      recipients: TEST_RECIPIENTS,
+      sender: TEST_SENDER,
+      wysiwyg: '<script>alert("xss")</script><p>Safe content</p>',
+    })
+
+    expect(html).not.toContain('<script>')
+    expect(html).not.toContain('alert("xss")')
+  })
+
+  it('should reject if both content and wysiwyg are missing', async () => {
+    await expect(
+      buildHtml({
+        content: [],
+        recipients: TEST_RECIPIENTS,
+        sender: TEST_SENDER,
+      }),
+    ).rejects.toThrow()
+  })
+
+  it('should reject with an invalid sender email', async () => {
+    await expect(
+      buildHtml({
+        content: ['Hello'],
+        recipients: TEST_RECIPIENTS,
+        sender: 'not-an-email',
+      }),
+    ).rejects.toThrow(EmailSchemaMessages.RECIPIENT_EMAIL)
+  })
+
+  it('should reject if recipients list exceeds 20', async () => {
+    const tooManyRecipients = Array.from({ length: 21 }, (_, i) => `user${i}@gmail.com`)
+
+    await expect(
+      buildHtml({
+        content: ['Hello'],
+        recipients: tooManyRecipients,
+        sender: TEST_SENDER,
+      }),
+    ).rejects.toThrow(EmailSchemaMessages.RECIPIENT_EMAIL_MAX)
+  })
+})
diff --git a/app/src/__tests__/send.test.ts b/app/src/__tests__/send.test.ts
index 780502f..c502922 100644
--- a/app/src/__tests__/send.test.ts
+++ b/app/src/__tests__/send.test.ts
@@ -10,7 +10,7 @@ describe('Send email test', () => {
       googleUserEmail: process.env.GOOGLE_USER_EMAIL || '',
       googleClientId: process.env.GOOGLE_CLIENT_ID || '',
       googleClientSecret: process.env.GOOGLE_CLIENT_SECRET || '',
-      googleRereshToken: process.env.GOOGLE_REFRESH_TOKEN || '',
+      googleRefreshToken: process.env.GOOGLE_REFRESH_TOKEN || '',
     }
 
     await expect(
diff --git a/app/src/__tests__/transport.test.ts b/app/src/__tests__/transport.test.ts
new file mode 100644
index 0000000..c162b3f
--- /dev/null
+++ b/app/src/__tests__/transport.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest'
+import EmailTransport from '@/lib/email/transport.js'
+
+describe('EmailTransport test', () => {
+  it('should initialize with a null transporter', () => {
+    const transport = new EmailTransport()
+    expect(transport.transporter).toBeNull()
+  })
+
+  it('should throw when getTransportOptions is called before createTransport3LO', () => {
+    const transport = new EmailTransport()
+    expect(() => transport.getTransportOptions()).toThrow('Transport not initialized')
+  })
+
+  it('should throw when googleUserEmail is not a valid email address', async () => {
+    const transport = new EmailTransport()
+
+    await expect(
+      transport.createTransport3LO({
+        googleUserEmail: 'not-an-email',
+        googleClientId: 'some-client-id',
+        googleClientSecret: 'some-secret',
+        googleRefreshToken: 'some-refresh-token',
+      }),
+    ).rejects.toThrow()
+  })
+
+  it('should have a non-null transporter after createTransport3LO with valid credentials', async () => {
+    const transport = new EmailTransport()
+
+    await transport.createTransport3LO({
+      googleUserEmail: process.env.GOOGLE_USER_EMAIL || 'user@gmail.com',
+      googleClientId: process.env.GOOGLE_CLIENT_ID || 'client-id',
+      googleClientSecret: process.env.GOOGLE_CLIENT_SECRET || 'client-secret',
+      googleRefreshToken: process.env.GOOGLE_REFRESH_TOKEN || 'refresh-token',
+    })
+
+    expect(transport.transporter).not.toBeNull()
+  })
+
+  it('should expose transport options after createTransport3LO', async () => {
+    const transport = new EmailTransport()
+
+    await transport.createTransport3LO({
+      googleUserEmail: process.env.GOOGLE_USER_EMAIL || 'user@gmail.com',
+      googleClientId: process.env.GOOGLE_CLIENT_ID || 'client-id',
+      googleClientSecret: process.env.GOOGLE_CLIENT_SECRET || 'client-secret',
+      googleRefreshToken: process.env.GOOGLE_REFRESH_TOKEN || 'refresh-token',
+    })
+
+    const options = transport.getTransportOptions()
+    expect(options).toBeDefined()
+    expect(options.host).toBe('smtp.gmail.com')
+    expect(options.port).toBe(465)
+    expect(options.secure).toBe(true)
+  })
+})
diff --git a/app/src/lib/email/sender.ts b/app/src/lib/email/sender.ts
index 14d6991..f25ae56 100644
--- a/app/src/lib/email/sender.ts
+++ b/app/src/lib/email/sender.ts
@@ -40,8 +40,14 @@ class EmailSender extends EmailTransport implements IEmailSender {
         throw new Error(EmailSchemaMessages.RECIPIENT_EMAIL_MAX)
       }
 
+      const from = transportOptions.auth?.user || process.env.GOOGLE_USER_EMAIL
+
+      if (!from) {
+        throw new Error(TransportMessages.MISSING_SENDER_EMAIL)
+      }
+
       return await this.transporter!.sendMail({
-        from: transportOptions.auth?.user || process.env.GOOGLE_USER_EMAIL,
+        from,
         to: receivers,
         subject,
         ...(!isHtml && { text: content }), // Text email
@@ -61,4 +67,8 @@ class EmailSender extends EmailTransport implements IEmailSender {
   }
 }
 
+const TransportMessages: Record<string, string> = {
+  MISSING_SENDER_EMAIL: 'Sender email address is not set. Ensure GOOGLE_USER_EMAIL is defined or pass it via oauth2 options.',
+}
+
 export default EmailSender
diff --git a/app/src/lib/email/transport.ts b/app/src/lib/email/transport.ts
index 25b7e46..48479a9 100644
--- a/app/src/lib/email/transport.ts
+++ b/app/src/lib/email/transport.ts
@@ -39,7 +39,7 @@ class EmailTransport implements IEmailTransport {
         googleUserEmail: options?.googleUserEmail || process.env.GOOGLE_USER_EMAIL,
         googleClientId: options?.googleClientId || process.env.GOOGLE_CLIENT_ID,
         googleClientSecret: options?.googleClientSecret || process.env.GOOGLE_CLIENT_SECRET,
-        googleRereshToken: options?.googleRereshToken || process.env.GOOGLE_REFRESH_TOKEN,
+        googleRefreshToken: options?.googleRefreshToken || process.env.GOOGLE_REFRESH_TOKEN,
       }
 
       this.#schema?.validate({ data: inputData })
@@ -53,7 +53,7 @@ class EmailTransport implements IEmailTransport {
           user: inputData.googleUserEmail,
           clientId: inputData.googleClientId,
           clientSecret: inputData.googleClientSecret,
-          refreshToken: inputData.googleRereshToken,
+          refreshToken: inputData.googleRefreshToken,
         },
       })
     } catch (err: unknown) {
diff --git a/app/src/scripts/cli/lib/handleHtml.ts b/app/src/scripts/cli/lib/handleHtml.ts
index 2f28d51..81720ca 100644
--- a/app/src/scripts/cli/lib/handleHtml.ts
+++ b/app/src/scripts/cli/lib/handleHtml.ts
@@ -10,42 +10,35 @@ export const handleSendHtmlEmail = async (options: EmailHtmlOptions) => {
     throw new Error('GOOGLE_USER_EMAIL .env variable is required')
   }
 
-  try {
-    const {
-      subject,
-      content: paragraphs = [],
-      recipients = [],
-      wysiwyg = null,
-    } = options
-
-    if (paragraphs.length === 0 && typeof wysiwyg !== 'string') {
-      throw new Error('One of content or wysiwyg is required')
-    }
-
-    // Clean data of whitespace
-    const emails = recipients.map(email => email.trim())
-
-    console.log(`Sending email to (${emails.length}) recipients`)
-
-    const emailContent = await buildHtml({
-      content: paragraphs,
-      recipients: emails,
-      sender: process.env.GOOGLE_USER_EMAIL,
-      wysiwyg,
-    })
-
-    await send({
-      subject,
-      content: emailContent,
-      recipients: emails,
-      isHtml: true,
-    })
-  } catch (err: unknown) {
-    if (err instanceof Error) {
-      console.log('[ERROR]: handle HTML email')
-      throw err
-    }
+  const {
+    subject,
+    content: paragraphs = [],
+    recipients = [],
+    wysiwyg = null,
+  } = options
+
+  if (paragraphs.length === 0 && typeof wysiwyg !== 'string') {
+    throw new Error('One of content or wysiwyg is required')
   }
 
+  // Clean data of whitespace
+  const emails = recipients.map(email => email.trim())
+
+  console.log(`Sending email to (${emails.length}) recipients`)
+
+  const emailContent = await buildHtml({
+    content: paragraphs,
+    recipients: emails,
+    sender: process.env.GOOGLE_USER_EMAIL,
+    wysiwyg,
+  })
+
+  await send({
+    subject,
+    content: emailContent,
+    recipients: emails,
+    isHtml: true,
+  })
+
   console.log('Process success')
 }
diff --git a/app/src/types/email.schema.ts b/app/src/types/email.schema.ts
index c358028..f7825b2 100644
--- a/app/src/types/email.schema.ts
+++ b/app/src/types/email.schema.ts
@@ -19,7 +19,7 @@ interface IOptionalParams {
  * Base schema for email validation within the `EmailTransport.sendEmail()` method
  * @property {string} [recipient] - (Optional) Email address of a recipient that will receive an email. Required if `recipients[]` is undefined.
  * @property {string[]} [recipients] - (Optional) Array of one or more email addresses of recipients that will receive an email. Required if `recipient` is undefined.
- * @property {string} subject Email message title (max 100 characters)
+ * @property {string} subject Email message title (max 200 characters)
  * @property {string} content Email message content can be a simple text or HTML string (max 1500 characters)
  */
 export const BaseEmailSchema = z.object({
@@ -57,7 +57,7 @@ export const EmailSchema = BaseEmailSchema.refine(
  * @typedef {object} EmailSenderType
  * @property {string} [recipient] - (Optional) Email address of a recipient that will receive an email. Required if `recipients[]` is undefined.
  * @property {string[]} [recipients] - (Optional) One (1) or more comma-separated email addresses of recipients that will receive an email. Required if `recipient` is undefined.
- * @property {string} subject - Email message title (max 100 characters)
+ * @property {string} subject - Email message title (max 200 characters)
  * @property {string} content - Email message content can can be a simple text or HTML string (max 1500 characters)
  * @property {boolean} isHtml - Flag indicating if the `content` field is in HTML format. Defaults to `false`.
  */
diff --git a/app/src/types/schemavalidator.interface.ts b/app/src/types/schemavalidator.interface.ts
index 6e64128..de8c518 100644
--- a/app/src/types/schemavalidator.interface.ts
+++ b/app/src/types/schemavalidator.interface.ts
@@ -61,9 +61,9 @@ export interface ISchemaValidator {
   /**
    * @description Get the base `ZodObject` schema from a `ZodEffects` schema
    * @param {ZodSchemaType} schema - The `ZodEffects` schema to get the `ZodObject` base schema from
-   * @returns {ZodObjectBasicType | null} The base schema or null if it's not a ZodEffects
+   * @returns {ZodObjectBasicType} The base schema
    */
-  getBaseSchema (schema: ZodSchemaType): ZodObjectBasicType | null;
+  getBaseSchema (schema: ZodSchemaType): ZodObjectBasicType;
 
   /**
    * Retrieves only the base `ZodObject` subset from `this.schema` using `.pick()`. Finds the base `ZodObject` if `this.schema` is a `ZodEffects` schema.
diff --git a/app/src/types/sender.interface.ts b/app/src/types/sender.interface.ts
index f1461c7..713acd0 100644
--- a/app/src/types/sender.interface.ts
+++ b/app/src/types/sender.interface.ts
@@ -1,14 +1,15 @@
 import type { EmailType } from '@/types/email.schema.js'
+import type { SentMessageInfo } from '@/types/transport.types.js'
 import SchemaValidator from '@/lib/validator/schemavalidator.js'
 
 export interface IEmailSender {
   /**
    * Sends an email using Gmail SMTP and Google OAuth2
    * @param {EmailType} params Input parameters for sending email
-   * @returns {Promise<void>} Resolved Promise that sent the email
+   * @returns {Promise<SentMessageInfo>} Resolved Promise with Nodemailer send result
    * @throws {ZodIssue[]} Input parameter validation error/s
    */
-  sendEmail (params: EmailType): Promise<void>;
+  sendEmail (params: EmailType): Promise<SentMessageInfo>;
 
   /**
    * Retrieves the email sender's local zod schema wrapper
diff --git a/app/src/types/transport.schema.ts b/app/src/types/transport.schema.ts
index 53e4d52..ce48d62 100644
--- a/app/src/types/transport.schema.ts
+++ b/app/src/types/transport.schema.ts
@@ -8,7 +8,7 @@ export const TransportOath2Schema = z.object({
   googleUserEmail: z.string().email().max(150),
   googleClientId: z.string().max(200),
   googleClientSecret: z.string().max(200),
-  googleRereshToken: z.string().max(500),
+  googleRefreshToken: z.string().max(500),
 })
 
 export type TransportOath2SchemaType = z.infer<typeof TransportOath2Schema>;