I'm in the process of moving around 30.000 emails from an Office 365 account to a free Gmail account. I tried several ways to do this:
- Copying emails in Outlook 2016 for Mac from the original folder in the Office 365 account to the destination folder in the Gmail account;
- Copying emails in Thunderbird for Mac from the original folder in Office 365 account to the destination folder in the Gmail account;
- Having Gmail fetch the messages to the Office 365 account root folder by POP access.
In all cases, for older emails previous to 2007 or so, the messages in Gmail appear only in text format and with the message: "This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible."
Is there a way to move the messages and have them show up in html in Gmail?