Windows 10 Windows Mail App with EAS (ActiveSync) issue causes emails not being sent and disappear

[nqservices]

Hi,

When using Windows 10 Mail App with an e-mail account setup using EAS ActiveSync, if we send some emails in a fast way (2/3 seconds between them) some of the emails will not be sent and will simple disappear.

To reproduce the issue, follow the bellow steps:

1. Add an email account using EAS ActiveSync protocol.
2. Send 6 emails in a fast way (2 or 3 seconds max time between them).
3. Check the sent folder. You will see that some emails are missing.
4. You can also check the recipient email address to confirm you did not receive all the emails.

NOTE 1: I have made the same test using IMAP and the issue does not happen. It only happens with EAS ActiveSync.

Can anyone please test from your end to confirm if this is a bug? Also, anyone here from Microsoft support?

Need help resolving this issue.

Thanks

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