Short answer: A connection issue or a large attachment can stop a message from sending.
Try these steps
- Confirm the internet works and check whether the mail app is offline.
- Review the attachment size and try a small message without an attachment.
- Check webmail for the same account and record any delivery error.
When to ask for help
Repeatedly pressing Send can cause duplicates. Do not delete the only copy of an important draft before saving it.
Learn more
Learn more: read this article — Microsoft: Fix sending and receiving in Outlook. Menu names and available features can vary by device, software version and account type.
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