Chapter 1 of 5 · Sort the problem first
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File verification needs a paid account.
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Sort the problem first
One message won't leave Gmail. Another left, and landed in Junk Email in Outlook. They look alike, but the fixes are completely different. A stuck Gmail message usually falls into one of four buckets. The connection. The message itself. The app or browser. Or the sign-in. Decide which one before you clear anything. The symptom points the way. Fails only on weak Wi-Fi? Change networks. Fails only with a file attached? Remove it. Gmail on the web won't send? Check Offline Mail, then try another browser. Web works, but Outlook or Apple Mail doesn't? Reconnect the account.
Fix the Gmail Outbox
On the web, start with Offline Mail, because it can hold messages locally. Open the gear icon, then See all settings, then the Offline tab. Turn off Enable offline mail, save, and refresh. Then send yourself a short plain-text test. Next, the file. Gmail's usual attachment limit is twenty-five megabytes, and encoding makes a file bigger in transit than it looks on disk. Remove the attachment and send. If it goes, share the file by cloud link instead. Still stuck? Suspect the message itself. Signatures pasted from Word, broken inline images and copied HTML can produce a message that won't send. Start a new draft with one line of plain text. If that goes, rebuild from there. If Gmail on the web sends fine, but Outlook, Thunderbird or Apple Mail doesn't, look at permissions. The app can keep showing mail after its sending permission has expired. Remove the account, revoke access in your Google security settings, then add it again. On Android, open the Gmail app settings, pick the account, then Data Usage. Turn Sync Gmail off, restart the phone, and turn it back on. Then check background data and battery limits. An inbox that loads doesn't prove sending works.
Find it in Outlook
Now the other problem. The message left, and it never reached the inbox. In Outlook, stop looking for a folder called Spam. It's called Junk Email. And check it under the right account. Found it? Move it to the Inbox. Mark it Not Junk if Outlook offers that. Add a sender you rely on to your safe senders. Then watch the next few messages, because one correction won't settle it. If it isn't in Junk Email either, and this is a company mailbox, there's another layer. In Microsoft 365, Defender can hold a message in quarantine, before it ever reaches the mailbox. Users may not see that.
If you're the sender
Ask your admin to check. If your own campaigns keep landing in Junk, that's a sender problem. Filters respond to trust signals. Dirty lists and repeated bounces teach providers to distrust you. Authentication alone won't fix that. BillionVerify won't unstick a Gmail draft. It works on the other side, checking addresses before a campaign goes out. Single checks work with your free daily credits, and our deliverability test is free. Verifying a file needs a paid account. Before sending, fix the client. After sending, fix the trust. Know which one you're looking at.
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20 free credits every day you use your account, up to 600 a month. No credit card required. Start at billionverify.com.
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