Enhancement: add text/plain version in mail notification to avoid be classified as spam

[butlerfr]

Hello

For some mail providers (hotmail/office365), mails send by sonerezh are considered as spam.
There is no problem with my mail configuration: I'm using SPF + DKIM with postfix.

Here is the return of spam assassin :
-1.105 | MIME_HTML_ONLY | Message only has text/html MIME parts

It should be very easy to fix by adding a simple text/plain version of the mail.

the complete report of spam assassin:

-0.1		DKIM_SIGNED		Message has a DKIM or DK signature, not necessarily valid
0.1		DKIM_VALID		Message has at least one valid DKIM or DK signature
0.1		DKIM_VALID_AU		Message has a valid DKIM or DK signature from author's domain
0.1		DKIM_VALID_EF		Message has a valid DKIM or DK signature from envelope-from domain
-0.001		HTML_MESSAGE		HTML included in message
-1.105		MIME_HTML_ONLY		Message only has text/html MIME parts
0.001		SPF_PASS		SPF: sender matches SPF record