---
title: Why are my SMTP emails not being delivered?
description: "Work through these in order. Most SMTP problems are a wrong port, a wrong username, or a sender address the provider hasn't verified. ## 1. Run Test Connection Open **White Label > Email Configs > SMTP Connectivity** and click **Test…"
url: "https://www.smsgatewaycenter.com/blog/kb/why-are-my-smtp-emails-not-being-delivered/"
updated: "2026-09-25"
category: Resellers / Email Settings
---

# Why are my SMTP emails not being delivered?

Work through these in order. Most SMTP problems are a wrong port, a wrong username, or a sender address the provider hasn't verified.

## 1. Run Test Connection

Open **White Label > Email Configs > SMTP Connectivity** and click **Test Connection**. A working setup returns **SMTP Connected**. Anything else points to the host, port, encryption or credentials.

## 2. Check the usual mistakes

| Symptom | Likely cause |
| --- | --- |
| Connection times out | Wrong port, or the port is blocked. Try 465 with SSL or 587 with STARTTLS. |
| Authentication fails | Wrong password, or a provider that needs an app password rather than the mailbox password. On AWS SES, the username must be the SMTP username starting with `AKIA…`, and the From E-Mail must be a separately verified address. |
| Authentication still fails with correct details | Set **SMTP Auth Mode** to LOGIN or PLAIN instead of Default (automatic). |
| Test passes but mail never arrives | The provider is rejecting the sender. Verify the From E-Mail with your provider and add SPF and DKIM records to your domain. |
| Some emails arrive, bulk sends stop midway | You are exceeding your provider's rate limit. Pick a lower **SMTP Provider Profile**. |

## 3. Has your SMTP been switched off automatically?

To protect your mail account from being locked by the provider, SMTP sending is **disabled automatically after five consecutive authentication failures**, and a notification email is sent to your registered reseller address. While it is disabled, **your users receive no emails at all**, including login OTPs and signup codes, so fix it as soon as you see that notice.

To restore it: open the SMTP Connectivity section, correct the credentials, and run **Test Connection**. A successful test clears the failure count and re-enables sending.

## 4. Still stuck

Contact support with the exact error from Test Connection, your SMTP host and port, and the time of a failed send, so the mail logs for your account can be checked.

### More Related Articles

- [How does email verification work when someone signs up on my white-label site?](https://www.smsgatewaycenter.com/blog/kb/how-does-email-verification-work-when-someone-signs-up-on-my-white-label-site/)
- [How do my users receive a login OTP by email?](https://www.smsgatewaycenter.com/blog/kb/how-do-my-users-receive-a-login-otp-by-email/)
- [How do I brand the emails my users receive?](https://www.smsgatewaycenter.com/blog/kb/how-do-i-brand-the-emails-my-users-receive/)

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