Verifying QQ Mail addresses

• Connections from outside mainland China are often refused, reset or left to time out, so the common result is no answer rather than a wrong one.
• Where a probe does complete, unknown recipients can return a 550, but the sample that gets that far is not representative.
• QQ numeric addresses use the account's QQ ID as the local part, which means the address is a digit string rather than a name.
• Foxmail addresses are aliases on the same accounts, so the two domains are one user base.

• Sending commercial mail into China carries regulatory requirements that sit well outside deliverability practice. Check them first.
• Tencent's filtering is opaque with effectively no postmaster tooling for foreign senders.
• Numeric local parts break naive validation rules that expect a name-shaped address, so check your own signup form accepts them.

Say you come home from a sourcing fair with 600 business cards typed into a sheet, and 410 of the addresses end in qq.com. You run the list, and the other 190 mostly resolve. All 410 QQ rows come back unknown, each with a timeout as the reason, and none of them are billed. It's tempting to call that a wasted run. What it told you is that two thirds of this list can't be checked by anyone probing from outside China, which is worth knowing before you plan a campaign around it.

The approach that works is slower and more reliable. Email the suppliers you care about one at a time from your normal mailbox, and see who replies. For a contact you met in person, the WeChat ID on the same card is usually the better channel anyway.

Start by asking where their probes originate. A verifier with servers inside mainland China can get real SMTP answers from Tencent, and that's a legitimate setup. If they probe from the US or Europe and still return valid and invalid on most QQ rows, ask what the verdict is based on. Pattern rules and old bounce databases are guesses, and they should be labeled as guesses.

Check the MX on Chinese company domains too. Tencent's business mail product hosts customer domains on hosts named mxbiz1.qq.com and mxbiz2.qq.com, so a supplier's own domain can face the same reachability problem as a personal QQ address. Don't test reachability from your office connection and draw conclusions. Most office and home networks block outbound port 25, so a failed telnet to mx3.qq.com usually tells you about your own internet provider and nothing about Tencent.