Email templates deliverability : MPART_ALT_DIFF


I am having some email deliverability issues lately. I have checked with my mail provider and with anti-spam testing services.

One of the issues that came up is that SpamAssassin lowers the score because of these two items :

  • MPART_ALT_DIFF : HTML and text parts are different (-0.7 points)
  • MIME_HTML_ONLY : Message only has text/html MIME parts (-0.1 points)

I have checked the source code of an email and indeed, it is sent as multipart/mixed, but it has in fact only a single non-empty part, of type text/html, and there is no text/plain part.

In the email template editor, I have not found any way to edit the text/plain message, and it does not seem that a stripped-down version of the HTML content is provided as text/plain content.

The result is that emails sent by Backendless applications are more likely to be considered as spam.

Have I missed something in the email template editor, or could you implement an HTML to text conversion so that emails may be more compliant ?


Hi @Nicolas_REMY ,

Sorry for inconvenience. Currently it is impossible to change this situation for emails formed from email templates since template itself handled on the server side as html. I have created an internal ticket BKNDLSS-33068 to adapt email sending logic to form emails which will be complient to rules which you mentioned.

As temporal solution and if it appliable in your case, you can try to use basic email sending logic and form emails in your code (client or server code). With this approach you will be able to eliminate MPART_ALT_DIFF rule violation. It is less convenient but it will increase email score for SpamAssassin.

Regards, Andriy

Hi @Andriy_Konoz ,

Thanks for the reply and for working on it.

Unfortunately, I can’t switch the logic. It’s in a mobile app that is already out there :slight_smile: And the app is sending the template.

Looking forward to a fix.

Hi @Nicolas_REMY,

The problem you wrote about above has been fixed on our side. We have added some changes to avoid the following issues with scores:


Can you confirm that everything is working as it should now?



Thanks a lot !
I will check and let you know if the issue persists.
Good job enhancing email deliverability !

@Nicolas_REMY, just would like to add. If you have an HTML_MIME_NO_HTML_TAG spam warning for an already created application, the following tags should be added to your email templates


Hi @Marina.Kan

Indeed I did get this error as well back then :sweat_smile:
I added the correct tags and this was corrected which increased deliverability a bit.
But thanks for the pointer. It might help others who may also get this issue !

@Nicolas_REMY, Have the overall scores improved for you now? Can I ask you to share with us the main points that affect your overall score? If the score is not satisfactory enough for you. We will see if there is anything else we can suggest or do.



I tested (using and can share the results with you. I have finally reached the maximum deliverability, thanks !

The points you solved were the last bringing me down somehow. So all is good now from what I can see, thanks.

@Nicolas_REMY, we are happy we were able to help you :slight_smile: