SOLVED IT.
You know what’s crazy ... I was going to send the list headers showing the difference between sending from Outlook and sending from Apple Mail, and I noticed that Outlook ALWAYS sends as multipart/alternative (sends both plain text AND html) ... whereas when I was sending just a test sentence with Apple Mail it only sent it as plain text which always failed. So I tested sending from Apple mail with something that would force it to send as multipart/alternative (I just bolded some text) and it PASSED DKIM every time I tested with something that forced Apple Mail to send as multipart/alternative. Then I saw this on the qmailtoaster wiki under DKIM: Testing DKIM signatures sending from Roundcube webmail I found that plain text formatted email caused DKIM failure sending to port25.com and GMAIL recipients, but when sending the same email in Roundcube's html format the DKIM signature was verified and passed. The same email DKIM signature passed with Squirrelmail, Thunderbird, and OpenDKIM's 'opendkim-testkey' program. It seems that certain email clients will add or subtract characters in the email header causing DKIM to fail. This may be happening in Roundcube while other clients do not affect the email header adversely. I have a help request in the Roundcube user's list for this issue. Hopefully, this issue is merely a configuration setting, if not, that it is resolved soon. And thought perhaps Apple Mail is also doing something to the email header ... so I looked in my signconf.xml file and saw my method was listed as “simple”. I changed it to “relaxed” and now the DKIM passes even when it is just plain text. Thank you to all who responded. From: xaf <[email protected]> Organization: ABAXE Reply-To: <[email protected]> Date: Friday, November 28, 2025 at 1:29 AM To: <[email protected]> Subject: Re: [qmailtoaster] Why does DKIM fail when I send with Mac Mail but passes with Outlook? So, can you share your Gmail inbox email sources? Open message > select three dots > Show Original. xaf Jaime Lerner a écrit le 27/11/2025 à 23:52 : It's just me sending an email to a gmail email address. On Nov 27, 2025, at 1:35 PM, xaf <[email protected]> wrote: Jaime Lerner a écrit le 27/11/2025 à 16:39 : Any ideas, anyone?? I'd like to switch to Mac Mail as my client, but have no idea why DKIM fails just because I'm sending with a different email client. I mean, isn't DKIM signed in the server?? Can you share the email sources from the recipient's inbox? xaf --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
