feat: Add Additional SMTP Headers to Decrease Spam Score

[michael-genson]

What type of PR is this?

(REQUIRED)

• bug
• feature

What this PR does / why we need it:

(REQUIRED)

Adds missing headers detailed in #2993 (and #3028) to decrease our spam score

Which issue(s) this PR fixes:

(REQUIRED)

Closes #2993
Fixes #3028

[Kuchenpirat]

Looks good 👍

[be-joeri]

Hi!

Thanks for implementing this, spam score looks much better now.

Two remarks:

• the message ID is missing brackets (< >), guess you can just add them when you generate the message_id variable on lines 48 and 52.
• the plain text part is shown in mail clients following RFC 2046 (Gmail for example). The last part of a multipart message is considered best and is preferred, so you should add the text part first and the html part second. You can fix this by swapping lines 44 and 45.

Keep up the good work!

[boc-the-git]

Hey @be-joeri, good detailed feedback there, thanks. This sounds like a great opportunity to get your first PR merged! :)
The README has a section on contributing as a starting point if needed, and we welcome all the help!
The Discord is also very friendly if you had a specific thing you needed help with while working through the process.

[be-joeri]

Hi @boc-the-git,

Thanks for suggesting to create a PR.
I'm not really a coder and the whole process is new to me, so reading instructions and setting things up took a lot more time than the actual change :)
I created #3094 . Please let me know if I made a mistake somewhere so I can take that into account next time.

[boc-the-git]

Well done @be-joeri!! First PR is a great milestone. Hopefully the first of many (be they for Mealie or other projects).

Given you mention your lack of familiarity with doing stuff like this, if there's anything in the docs that could be made more clear, from your experience, please let us know!