Skip to main content

How Can We Help?

< Back
You are here:
Print
Created On
Last Updated On
byMail250

This guide explains how to configure SendBlaster (v4) to send emails using Mail250 SMTP securely.

Before you start

Keep these details ready from your Mail250 account:

  • SMTP Host

  • SMTP Port

  • SMTP Username (full format)

  • SMTP Password

  • Allowed sender email (From address)

Recommended (working) values used in this guide:

  • SMTP host: smtp.swipemail.in

  • Port: 587

  • Security: STARTTLS (automatic in SendBlaster when SSL is unchecked)

  • Username example: SMTP_USERNAME@swipemail.in

Step 1: Open SendBlaster SMTP settings

  1. Open SendBlaster

  2. Click Send (left menu)

  3. In Send settings, select Use SMTP server

Step 2: Enter SMTP server details

In the SMTP section, fill these fields:

  1. SMTP server: smtp.swipemail.in

  2. Port: 587

  3. SSL: Unchecked

  4. Check: Authentication required

  5. Username: your full SMTP username (example: SMTP_USERNAME@swipemail.in)

  6. Password: your SMTP password

Important:

  • Do not use short usernames like SMTP_USERNAME

  • Use the exact username provided by Mail250

Step 3: Verify connection (Connection test)

  1. Click Connection test

  2. If you see “Connection established”, SMTP login is working.

If it fails, jump to the Troubleshooting section.

Step 4: Set sender details (From / Return-Path)

At the top of the Send screen:

  • Sender e-mail address: use your sender address (example: shipping@mail250.com)

  • Sender name: your brand or company name

  • ReturnPath (address for bounces): usually the same as sender email

Tip:
If sending fails later due to sender restrictions, test once using the same email as your SMTP username, then switch back.

Step 5: Recommended speed settings (avoid blocks)

SendBlaster can send too fast and trigger throttling. For stable sending, set safe values.

Go to Advanced settings → Timing and use:

  • Suggested settings: Normal

  • Connections: 1

  • Messages per block: 50 (or 100)

  • Pause between messages: 1 to 2 seconds

  • Pause between blocks: 10 seconds

  • Timeout: 60 seconds

After successful campaigns, you can increase gradually.

Step 6: Send a test email

  1. Create a small test list (1 to 3 recipients)

  2. Send a simple email with a basic subject like “Test”

  3. Confirm delivery in the inbox

Troubleshooting

Error: 530 5.5.1 Authentication Required

Meaning: SendBlaster is trying to send before logging in.

Fix:

  • Ensure Authentication required is checked

  • Ensure Username and Password are filled

  • Use Port 587 and keep SSL unchecked

Error: 334 (during authentication)

Meaning: The server is asking for username or password during AUTH LOGIN. This is normal, but if it fails after 334, credentials are wrong.

Fix:

  • Use the full SMTP username (example: SMTP_USERNAME@swipemail.in)

  • Re-enter the password carefully (avoid extra spaces)

  • Use Port 587 and SSL unchecked

Error: 535 Authentication failed

Meaning: Username or password is incorrect.

Fix:

  • Confirm the exact SMTP username from Mail250

  • Reset SMTP password in Mail250 and update in SendBlaster

  • Try Connection test again

Error: 550 or 553 Sender rejected / not allowed

Meaning: Your From address is not permitted by the SMTP server.

Fix:

  • Test sending once with From email same as SMTP username

  • Ask Mail250 support to allow or verify your domain and sender (example: bulkcom.com)

Best practice for new accounts (warm-up)

If this is a new domain or new SMTP account, scale slowly:

  • Day 1: 50 to 100 emails

  • Day 2: 200 to 300 emails

  • Day 3: 500 to 800 emails

  • Then increase gradually

byMail250
Table of Contents