It usually means your email draft was changed after Outlook or your mail app opened it, so the app refuses to send the older version. In practice, this is often a sync or draft-conflict issue, especially in Outlook and IMAP accounts.

What it means

The app thinks the message you’re trying to send is no longer the same message you started composing. That can happen if the draft autosaved, the message was reopened in another window, an add-in edited it, or the mailbox didn’t sync cleanly.

Common fixes

  • Close the draft and reopen it, then try sending again.
  • Copy the email text into a brand-new message and send that.
  • Make sure Outlook is fully updated.
  • Restart the app and your computer.
  • If you use Outlook, check whether the issue happens in webmail too; if it only happens in the desktop app, the local profile or settings are more likely the cause.

Outlook-specific fix

A commonly reported fix is to turn off the Conversation Clean Up option: File > Options > Mail > Conversation Clean Up > When a reply modifies a message, don’t move the original. Several users report that changing this setting stops the error.

If it keeps happening

If the problem continues, the next likely causes are a damaged Outlook profile, a sync problem with IMAP/Exchange, or an add-in conflict. In that case, repairing Office, creating a new profile, or testing Outlook in safe mode are typical next steps.

Bottom line: it’s usually not saying your email content is wrong; it’s saying the draft changed after it was first loaded, so the app won’t send that version.