I'm trying to send email using Power Automate and the Graph API in MIME format. If I encode the email externally, it works fine but if I encode it using the encode64 function in Power Automate it throws an error `invalid base 64 string for MIME content`.
In the flow, there is an action containing the MIME string data, followed by two parallel branches. One Compose encodes the MIME data `base64(outputs('Compose_MIMEType'))` while the one in the parallel branch uses the already encoded string.
I used https://www.base64encode.org/ to encode it online in UTF-8 and LF (Unix) options. However I also tried it from https://base64.guru/converter/encode using "Base64 Standard = Main" and "Character Encoding = UTF-8" which resulted in a different Base64 encoded string that also worked fine.
Those are followed by two Outlook Send an Http Request actions which each respectively send the base64 encoded strings.
There does not appear to be any difference between the two encoded strings after a character/character comparison but the action using the Power Automate encoded string fails.
Here is the test email I'm using
To: me@gmail.com
Subject: Concert!
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="frontier"
--frontier
Content-Type: text/plain
Hey Jane,
Let's go as a team next Friday.
Depeche Mode concert!
--frontier
Content-Type: text/html
<html>
<body>
<p>Hey Jane,</p>
<p>Let's go as a team!</p>
<p>Depeche Mode concert next Friday.</p>
</body>
</html>
--frontier--
Base64 Encoded via online
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
Base64 encoded via Power Automate
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
Error
{
"error": {
"code": "ErrorMimeContentInvalidBase64String",
"message": "Invalid base64 string for MIME content."
}
}What am I missing? Is anyone else experiencing anything similar?
