Outlook sending sometimes vertical bar

Hi,

have troubles with my outlook (office365). Sending about 30-40 e-mail per day. And after email sent where I go to the sent folder sometimes instead of content I wrote I can see something like:

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So basicly it's replacing my content to IIIII keyboard characters | vertical line. My clients gets IIII instead of content I wrote and than I have to write all again. It happens not too often, but I've tried reisntall outlook and clear cache/wipe etc. It's like 1 or 2 e-mail per 50/60 crashed. Sometimes full week is OK and than it's fail. Not sure what can I do. I've tried search similar problem - but this is I think very rare.

Br,

Greg