fix : Ipv6 pref sending if available

[frju365]

AW: I just added the solution provided by @jershon

The problem

For SPF record :
As I understood, it could be problem if main domain (exemple for a website) has different ipv4 than actual mail server.

For ipv6 :
Some email provider communicate only in ipv6. Apparently following issue this can be a solution of not receiving mail on some email hosting providers.

Related issues: : fixes YunoHost/issues#2465
Related PRs:

Solution

• add preference to ipv6 if avilable
• Correct SPF record. Allow domain to be handle by server IP even if main site is no handle by server.

AI transparency: Understand difference between record (I didn't fully remember what was the good way to handle such case).

PR Status

Tested partially

Code TODOs

Here are frequently forgotten tasks:

• Discuss about this change with others contributors (on chat, contributors meeting, forum, issues or pr)
• Update related repo (like yunohost-admin, yunohost-portal, package-linter, etc.)
• Write data or settings migration
• Pass Continuous Integration checks
  • Add some missing translations keys
  • Update/write unit tests
• Update/write documentation

Tests TODOs

Indicate here tests you have already done, and tests you think should be done

• Run the code in cli by calling command by hand
• Test change on configuration on an instance

How to test

Please add here commands to install dependencies, manual change to do in ynh-dev container, commands to make some basic tests, etc.
...

[zamentur]

The issue 2465 seems not about distinct mail and web server for a same domain.

[zamentur]

a already means AAAA if the mail is sent with ipv6.

SO for me the only reasons to add this, is the case where no MX or A records exists for the IP of the server. This happens if mail_in is disabled and if a website is hosted on the domain on another host.

https://github.com/Nerteron/yunohost/blob/12c2594b1024a604d5bd3d96007b79905d4de87d/src/dns.py#L207

I think there could be a lot of situations for which SPF should be customized, the important thing is to check with diagnosis that current IPs are allowed.

For me this part should be in another PR , maybe with a settings to include a custom part to SPF

[zamentur]

Suggested change

	# Tentative de mitigation en cas où le serveur du domaine d'envoi du mail est différent
	# du serveur du domaine (site externalisé) Issue: #2465
	spf4 = ""
	spf6 = ""
	if ipv4:
	spf4 = ' ip4:' + ipv4
	if ipv6:
	spf6 = ' ip6:' + ipv6
	mail.append((basename, ttl, "TXT", f'"v=spf1 a mx{spf4}{spf6} -all"'))
	mail.append((basename, ttl, "TXT", '"v=spf1 a mx -all"'))

[zamentur]

I suggest to remove the SPF part