How to change the default DKIM selector

[vasg]

Yes, it was later discovered that if only change /etc/opendkim/KeyTable, this will not last for a long time, it will automatically return to the mail selector
Therefore, we need to create a new file /etc/opendkim/KeyTable_new：

example.com example.com:box:/home/user-data/mail/dkim/mail.private

We can also change the location of /home/user-data/mail/dkim/mail.private if we want
However, we cannot changed the file name of /home/user-data/mail/dkim/mail.txt, but we can change its content, which is displayed on the External DNS section of the website

Finally change the /etc/opendkim.conf file:
replace KeyTable refile:/etc/opendkim/KeyTable
to KeyTable refile:/etc/opendkim/KeyTable_new

Then
sudo service postfix restart
sudo service opendkim restart

[miaber]

@vasg

Yes, it was later discovered that if only change /etc/opendkim/KeyTable, this will not last for a long time, it will automatically return to the mail selector
Therefore, we need to create a new file /etc/opendkim/KeyTable_new：

example.com example.com:box:/home/user-data/mail/dkim/mail.private

1. Any idea what is overwriting /etc/opendkim/KeyTable?
2. If we use /etc/opendkim/KeyTable_new, will it reflect newly added domains?
3. Will these changes persist after an MIAB update?

I have an issue here and GMail is complaining my DKIM fails

Suppress/re-classify MX errors

This domain’s DNS MX record is incorrect. It is currently set to ‘10 mail.example2.com’ but should be ‘10 box.example.com’. Mail will not be delivered to this box. It may take several hours for public DNS to update after a change. This problem may result from other issues listed here. I would like to use MIAB as a send only server, so my MX record is configured differently to what MIAB expects and is causing MIAB to report the error above. Can I make MIAB suppress/re-classify the above erro…

[KiekerJan]

@miaber

I have an issue here and GMail is complaining my DKIM fails

Before you dig into this, you have to think about why going this route will solve your problem. What error is GMail giving?

1. Any idea what is overwriting /etc/opendkim/KeyTable?
2. If we use /etc/opendkim/KeyTable_new, will it reflect newly added domains?
3. Will these changes persist after an MIAB update?

There’s code in the mailinabox daemon that updates the file. The following Pull request contains all changes necessary to add a second selector, which should give you an idea of the impact. Note that it also replaces opendkim with dkimpy, so it does more than necessary to add a selector.
If you don’t change the code, the maintenance code will overwrite the changes you make to the KeyTable file at least if something changes to the domains on the box.

[miaber]

1. It said mail was rejected because sender must be authenticated using SPF or DKIM
2. My DNS currently already has mail._domainkey... defined for another sender, DKIM will never pass
3. I managed to add a custom selector and mails have been accepted by gmail
4. What I need now is a proper solution

[KiekerJan]

Regarding 2: you might be able to reuse the dkim keys? That is, use the same on both senders. But you might not want that, or perhaps your other sender is rotating keys?

So assuming you have it all working: your concern is the overwriting of the Keytable file? You can use a Keytable_new file by changing the configuration in /etc/opendkim.conf: ‘KeyTable refile:/etc/opendkim/KeyTable_new’
This change is (currently) not overwritten on a mainabox update.

If something changes in the Keytable file because you added or removed domains, you need to add them yourselves to the Keytable_new file.