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If something isn’t working as expected, this guide covers the most common issues Sinosend users encounter — and exactly how to fix them. Work through the relevant section below, and if the problem persists, contact support for live assistance.

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Delivery issues

Follow these steps in order:
  1. Check spam and junk folders. Delivery notification emails occasionally get filtered — ask your recipient to search for an email from noreply@sinosend.com.
  2. Verify the email address. Open the transfer in your dashboard, go to the Recipients tab, and confirm the address is spelled correctly.
  3. Resend the notification. From the Recipients tab, select the recipient and click Resend notification. A fresh email will be dispatched immediately.
  4. Try an alternative email address. If the recipient uses a corporate mail server with aggressive filtering, ask them for an alternative address and add it as a second recipient.
If the email still doesn’t arrive after resending, contact Sinosend support. The team can check delivery logs and confirm whether the email was accepted by the recipient’s mail server.
Cross-border file delivery into China requires the correct routing. Check the following:
  1. Verify your data region. Open the transfer in your dashboard and confirm it was created with either the APAC Hong Kong or Mainland China (Shanghai) region. If it was sent using a different region, the transfer will need to be resent with the correct region selected.
  2. Try a different browser. Ask the recipient to try Chrome or Edge if they’re using another browser.
  3. Check for VPN interference. VPN software on the recipient’s device can interfere with downloads, particularly on Chinese mobile networks. Ask them to disable any active VPN and try again.
For recipients inside mainland China, Mainland China (Shanghai) consistently delivers the fastest speeds. Use APAC Hong Kong for recipients in Hong Kong, Taiwan, or nearby regions.
Slow downloads are almost always a network or region issue. Try these steps:
  1. Check the recipient’s network. Ask them to try on a different connection (e.g. switch from Wi-Fi to mobile data, or vice versa).
  2. Confirm the correct region is selected. For APAC recipients, make sure the transfer used the appropriate APAC or China region — a transfer routed through a European data centre will be noticeably slower for someone in Shanghai.
  3. Switch from in-browser preview to direct download. If the recipient is previewing a large file in the browser, ask them to click the Download button instead to use the full download speed rather than the streaming preview.
If a recipient reports that their link is no longer working, the transfer may have reached its expiry date. To restore access:
  1. Open the transfer from your dashboard
  2. Click Expiry
  3. Select a new expiry date and save
The recipient’s existing link immediately becomes active again — you don’t need to resend anything.
On all Sinosend plans, transfers do not expire by default. If your transfer expired, an explicit expiry date was set when it was created. You can disable expiry entirely using the Dynamic File Management settings.

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Upload issues

Sinosend uses resumable uploads — if your connection drops during an upload, it will automatically pick up from where it left off. If the upload appears stuck or shows an error:
  1. Refresh the page. The upload will resume from the last successfully uploaded chunk.
  2. Check your internet connection. Unstable connections on large files are the most common cause of mid-upload failures.
  3. Check your file size against your plan limit. Free: 5 GB, Personal: 10 GB, Pro: 25 GB, Business: 100 GB. Uploads that exceed your plan limit will be rejected before completing.
Do not close the browser tab while an upload is in progress. While resumable uploads protect against connection drops, manually closing the tab will interrupt the session.
If you receive a file size error, your file exceeds the limit for your current plan. You have two options:
  • Upgrade your plan to increase the per-transfer limit. Personal: 10 GB, Pro: 25 GB, Business: 100 GB.
  • Split the transfer. Compress and split the content into multiple transfers that each fit within your plan’s limit.
View and compare all plans to find the one that fits your file sizes.
Folder drag-and-drop upload is supported in Google Chrome and Microsoft Edge. If you’re using Safari or Firefox, you may encounter limited or no folder upload support.To work around this:
  1. Switch to Chrome or Edge and drag the folder directly into the upload area.
  2. Alternatively, compress the folder into a ZIP file and upload the single ZIP — this works in all browsers.
Safari on macOS has partial folder drag-and-drop support. If it’s not working, the most reliable fix is to use Chrome.

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Account issues

  1. Reset your password. Go to app.sinosend.com/forgot-password, enter your email address, and follow the instructions in the reset email.
  2. Check your spam folder. Password reset emails occasionally land in spam — search for an email from noreply@sinosend.com.
  3. Make sure you’re using the right email address. If you signed up with a Google or SSO account, try using the Continue with Google option instead of entering a password.
If none of the above work, contact support and the team will help you verify your identity and regain access.
  1. Check spam and junk folders for an email from noreply@sinosend.com.
  2. Resend the verification email. On the login page, look for the Resend verification email option.
  3. Check for typos in the email address you signed up with — log in and confirm the address shown in your profile settings.
If the email still doesn’t arrive after resending, contact Sinosend support. Corporate mail servers with strict filtering sometimes block automated emails outright.
If you’ve lost access to your 2FA device or authenticator app, email support@sinosend.com with the following:
  • The email address associated with your account
  • Your full name
  • Any recent transfer details (recipient email, file name, or date) to help verify ownership
The support team will verify your identity and restore access. For security reasons, 2FA recovery cannot be completed through self-service.
Never share your account password with the support team. Sinosend staff will never ask for it.

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Branded portal

If your branded portal isn’t loading on your custom domain, work through these checks:
  1. Verify your DNS CNAME record. Your domain’s CNAME record must point to portal.sinosend.com. Log in to your DNS provider and confirm the record is saved correctly.
  2. Wait for DNS propagation. DNS changes can take up to 48 hours to propagate globally. Use a tool like whatsmydns.net to check whether your CNAME has propagated in your region yet.
  3. Check for conflicting records. If you have an existing A record or CNAME for the same subdomain, remove it — conflicting records can prevent propagation.
  4. SSL certificate provisioning. Sinosend automatically provisions an SSL certificate once DNS verification is complete. If your domain shows a certificate error shortly after propagation, wait a few minutes and reload — this typically resolves automatically.
SSL is provisioned automatically after DNS verification. You do not need to upload a certificate manually.
White-label email delivery requires configuring SPF and DKIM DNS records on your domain so that emails can be sent on your behalf. Without these records, emails fall back to Sinosend’s own sending domain and branding.To set up white-label email:
  1. Go to your Branded Portal settings in the dashboard
  2. Locate the Email sending section and copy the SPF and DKIM record values
  3. Add both records to your domain’s DNS via your DNS provider
  4. Return to the dashboard and click Verify to confirm the records are live
For a full walkthrough, see the Branded Portals guide or contact support.
SPF and DKIM records can take up to 24 hours to propagate. If verification fails immediately after adding the records, wait an hour and try again.

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Contact support

Still stuck? The Sinosend support team is ready to help. Visit sinosend.com/support to start a live chat with the team — available 24/7 on all paid plans. You can also reach out on Twitter / X at @sino_send, or browse video walkthroughs on the Sinosend YouTube channel.