email.utils.make_msgid return ids that break email messages with related content

Bug report

I have been trying to replicate the examples listed here: https://docs.python.org/3/library/email.examples.html

For some reason the one about "creating an HTML message with an alternative plain text version" is assembling an email message that Thunderbird (and other email readers) does not display correctly, as images are not displayed and marked as broken.

The example uses make_msgid() to generate content ids.

Python 3.10.9 (main, Dec  7 2022, 03:14:04) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from email import utils
>>> utils.make_msgid()
'<167119948916.50921.14529814791249370642@1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa>'
>>>

Turns out that for some reason the string is too long, because if I either remove the domain part or purportedly shorten it, e.g., make_msgid(domain="0.0.0.ip6.arpa"), then everything works again and the resulting email can be correctly displayed in Thunderbird/Outlook.

Your environment

• CPython versions tested on: 3.10.9
• Operating system and architecture: OSX/M1

Linked PRs

• gh-100856

Start by reproducing the Thunderbird/Outlook failure from the email.examples.html example and inspect email.utils.make_msgid(), especially with its default domain. Compare the generated content IDs with the shortened-domain case; done means the example produces related-content messages that email readers display correctly.