HTML mails not sent out properly

There has been no effort made yet in the simplenews - mimemail cooperation. Therefore I mark this as a feature request.
The cause of your problem is not necessarily in simplenews. The mimemail conversion to 6.x is still in an very early stage and currently my priorities are to finalize the simplenews 'stand alone' features.

Feel free to further investigate the cooperation between mimemail and simplenews. Patches are welcome!
What mimemail receives (and simplenews generates) is in the $message variable in the various mail functions:
drupal_mail()
simplenews_mail()
drupal_mail_send()
mimemail_mailengine()
mimemail_mail_alter()

Thanks for stepping forward and working on this part! You are the first one to test, since it is the first piece of working 6.x mimemail. Hardly no mimemail integration is available in simplenews yet. Based on your above mentioned code I will investigate it.

I did a bit of playing and got html mail working with mimemail for the cron emails. It checks for the mimemail module and also checks to see if the format is html or plain. This code would need to be used in other places, but I thought a good start would be to test it in cron. We could make this code a method that other places emails are sent can easily call.

Sorry if I jumped in on this, but I have a few people who want this functionality.

I will wait until a drupal 6 compatible version of mime mail is available before I commit a mimemail integration of simplenews. But that should not hold us back to work on code for it.

For The Youthie (a Tamworth Regional Council Youth Centre, NSW, Australia) I am working on an implementation of mimemail and simplenews for their Drupal 6 site. The code is in testing phase and will be published here when finished.

the confirmation messages is also wont send by mime and they are in plain text format

For those who can not wait for mimemail to get moving and need to get a working simplenews HTML mail solution, here is a patch (to HEAD) of the work I did for The Youthie. Sponsored by Tamworth Regional Council Youth Centre, NSW, Australia.

This patch to simplenews must be combined with the following patches to Mimemail HEAD (revision 1.24):
Issue 259821: http://drupal.org/files/issues/mimemail.codestyle_HEAD.patch
Issue 195466, #16: http://drupal.org/files/issues/mimemail.upgrade02.patch

The attached patch will not be committed to Simplenews before at least a Drupal 6 compatible HEAD version of Mime mail is available.
Further requests for HTML support for simplenews 6.x is therefore useless. Simplenews will only support plain text until further notice.

The above patches were the result of a custom upgrade of mime mail and simplenews I did. I have no plans to keep he patches up to date with the Progress of Simplenews (unless I get a new job request).

I've tried the patches to get a working version of Simplenews with HTML on drupal 6.3, but I wasn't succesful...

I've applied the patch on Simplenews 6.x-1.0-beta1 (I didn't found any other versions the patch working with, so I thing the patch made for this version), there was no errors.

Also, I've downloaded the mimemail head and tried to apply the patches, but I don't know the tries was wrong or not...
I've tried to patch it with mimemail.codestyle_HEAD.patch first, then with mimemail.upgrade02.patch by -R option, which had 2 of the parts not applied. (I've also had other tries.)

Now, I cannot send news with simplenews module, because all the contents I try to send goes to Draft folder and get a red 'x' letter near it.

Other mails (for example, in the contacts field) still working in html.

What did I wrong?
I hope you can help me.

Thanks a lot.

Sorry, I do not support for this before at least a Drupal 6 compatible HEAD version of Mime mail is available

OK, sorry for my comment.
I just tried to regenerate the modules you worked on by apply the patches you submitted.

I think I didn't find the version of mimemail the submitted patches based on.
May you (or somebody) send the patched version somehow?

I really would like to use newsletters on a Drupal 6 site with a little html formatting...
It would be great if I can try the correctly patched module, maybe it would work for me also.

Sorry again.

See also the (duplicate) feature request at: http://drupal.org/node/287676

I updated #10 to apply to HEAD. A lot of code seems to have changed from when that patch was made, so much of my patch is new. I kept the code that sets $message['format'] in simplenews_mail(). But I took a slightly different approach with simplenews_backend_send(), and created simplenews_backend_mail() instead, which is a drop in replacement to drupal_mail() that automatically uses mimemail() when available. This simplified code, and doesn't require module_exists('mimemail') to be scattered everywhere. I then went through and replaced every instance of drupal_mail() with simplenews_backend_mail().

With this patch and my Mimemail patch, I've been able to send simple HTML messages, but I haven't yet tested with CSS or HTML.

This is my first time working with patches or contributing to Drupal, so let me know if I've done something incorrectly. I'd also take suggestions on a better way to implement mimemail, if perhaps there was some benefit to the simplenews_backend_send() approach that I didn't realize.

Looks like there is still work to do before an official Mimemail 6.x gets started, so I guess this is still postponed. I'm still using my patch for a usable mimemail + Simplenews on 6.x which I need now, so if anyone uses it and runs in to issues I'd certainly like to know and make a fix. But otherwise this won't be going in any time soon.

I've found this thread today again, and I tried matthewbot's patch to simplenews.
It looks very well.

I don't know which patch I've added to my mimemail module, but it seems now I can send my newsletters correctly.
I will test it a little bit more, but it could attach my images to the newsletter.
Maybe I had a little problem with permissions, because if I took the picture from my own directory, it never attached to the mail (I saw just it's place), but when I submitted the image with upload to a common space, it always attached it correctly, so I think it is not mimemail's problem.
(So, the images attached to the mail itself, and also it attached my smileys :) )

Also, I can switch between html and plain text mails without any problems (in the post newsletter section), it seems both are working.

Maybe one thing I will try to remove, the mail's subject appears also in the beginning of the mail... and I don't like it... :)
...but it is absolutely ok now.

I will test it a little bit, but it seems I can use it very well.
Thank you your works.

I just added another fix for Mimemail on that node, which was referenced earlier.

http://drupal.org/node/195466

This method (#10, #14) of solving the Mime Mail compatibility will not be implemented.
See http://drupal.org/node/305650 for the current solution.