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SYSTEM SETTINGSConfigure SMTP with Resend
Configuration guideAdmin guide

Configure SMTP with Resend

Connect Resend for ChatHub password resets, staff invitations and workflow emails: verify a domain, create an API key, configure SMTP and send a test.

ChatHub Team·6 min read

Before you start#

Email settings are shared by password resets, staff invitations and the Send email workflow step. Prepare a ChatHub account with permission to manage settings, a Resend account, a domain you own and access to its DNS settings.

noreply@example.com and support@example.com are examples only. Replace them with your own addresses. Keep real API keys out of source code, screenshots and support messages.

1. Verify your sending domain in Resend#

  1. 1

    Sign in to Resend, open Domains and add the domain or subdomain you will send from.

  2. 2

    Open the domain details and its Records tab. Add the exact DNS records Resend supplies at your DNS provider, matching each record type, name and value. Do not copy another domain’s example values.

  3. 3

    Select Verify DNS Records and wait for sending verification. If pending, check the records and allow time for updates. Continue once the domain is verified for sending.

  4. 4

    Choose a sender address on that verified domain. For example, use noreply@mail.example.com if you verified mail.example.com.

Resend: manage domains and DNS records ↗

Resend: verified domains ↗

2. Create an API key for ChatHub#

  1. 1

    Open API Keys in Resend and create a dedicated key named something recognizable, such as ChatHub SMTP.

  2. 2

    Choose Sending access and restrict the key to your sending domain when that option is available.

  3. 3

    Copy the key when it is created and store it securely. Resend does not show its value again. You will paste it into ChatHub’s Password field.

Resend’s SMTP password is your API key, not your Resend account password or a Gmail app password. Enter a new Resend key when switching from another provider.

Resend: manage API keys ↗

3. Complete ChatHub’s Email settings#

Open Administration → Settings → Email, or /settings?tab=email on your own ChatHub domain. In the SMTP panel, complete these fields (Vietnamese labels are included for reference):

  1. 1

    SMTP host (Máy chủ SMTP): smtp.resend.com, without https://.

  2. 2

    Encryption (Mã hoá): STARTTLS. Port (Cổng): 587.

  3. 3

    Username (Tài khoản đăng nhập): resend.

  4. 4

    Password (Mật khẩu): paste the Resend API key. If a password exists, the field is labeled New password (Mật khẩu mới); enter a new key to replace it.

  5. 5

    Sender name (Tên người gửi): your shop or brand name, for example ChatHub.

  6. 6

    From address (Địa chỉ gửi): an address on your verified domain. Replace the example noreply@example.com with your own address.

  7. 7

    Reply-to address (Địa chỉ nhận trả lời): a mailbox you monitor. Replace support@example.com with your real address. Leave blank if replies should go to the From address and it can receive mail.

  8. 8

    Turn on Enable email sending (Bật gửi email).

Figure 1. Vietnamese interface: select Email on the left and enter the host and username shown. Paste your Resend API key into Password on the right. This is an unsaved illustration with no real key.
Figure 2. Vietnamese interface: replace the example.com addresses with your own. From must use your verified Resend domain; Reply-to should be a mailbox you monitor. Enable email sending before saving. Values shown are unsaved examples.
Always fill in From address for Resend. If blank, ChatHub uses the SMTP username “resend” as the sender, which is not a valid email address. The general hint that the username is usually your email does not apply to Resend.

For port 465, select SSL/TLS instead of STARTTLS. Check both fields after changing encryption. Common pairs are STARTTLS + 587 or SSL/TLS + 465.

Resend: official SMTP settings ↗

4. Save, then send a test email#

  1. 1

    Review the settings and select Save (Lưu). Wait for “Đã lưu cấu hình email.” (Email configuration saved).

  2. 2

    In the test section, enter your own mailbox in Send to (Gửi tới). This sends a real email using the saved configuration.

  3. 3

    Select Send test email (Gửi thư thử), read the result and check the receiving mailbox, including spam. Verify the sender name, From address and Reply-to address.

  4. 4

    If the message has not arrived, open Emails in Resend to inspect the SMTP message and its status. ChatHub reporting a successful send does not guarantee inbox placement.

Figure 3. Vietnamese interface: select Save (Lưu) below first, then use Send to (Gửi tới) and Send test email (Gửi thư thử) above. The button is disabled because this illustration has not been saved. Replace your-email@example.com with your own mailbox. This is not a successful-send screenshot.
The test button is disabled until an SMTP host is saved and whenever configuration changes remain unsaved. Save after each settings or API key change before testing again. Configured only means an SMTP host has been saved; it does not confirm successful delivery.

ChatHub encrypts the stored password and never displays it again. Leaving New password blank keeps the existing password, so an empty field after saving is normal. Turning off Enable email sending and saving stops system emails while retaining the configuration.

5. Troubleshooting#

  1. 1

    Authentication rejected: check that the username is resend and the password is a valid API key with sending permission for the correct domain. Re-enter the key and save.

  2. 2

    Sender or domain error: ensure From address is present, valid, on your verified Resend domain and permitted by the key.

  3. 3

    SSL/TLS error: use STARTTLS + 587 or SSL/TLS + 465. Do not switch to unencrypted mode to resolve an error.

  4. 4

    Connection failure or timeout: check smtp.resend.com and outbound SMTP connectivity from the ChatHub server, including DNS, firewall and hosting restrictions.

  5. 5

    Not configured or disabled: check SMTP host, enable email sending and save.

  6. 6

    Recipient rejected or sending limit reached: read the error details and check the receiving address and your current Resend account limits.

  7. 7

    Sent but not received: inspect the message in Resend’s Emails page, check spam and the recipient address, then follow the status of that message.

This guide was checked against ChatHub’s Email interface and source code, and official Resend documentation. No API key was created, DNS changed, live settings saved or test email sent while preparing it.
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