I have a Google Apps account on primary.com. Recently I added secondary.com as an additional domain to primary.com's Google Apps account.
I then added an address @secondary.com to my account @primary.com and set it up as a "Send mail as" address in Gmail using smtp.gmail.com and firstname.lastname@example.org to authenticate via SMTP.
DKIM is set up for both primary.com and secondary.com for Google Apps.
When I send an email from email@example.com in Gmail the recipient sees: from firstname.lastname@example.org via primary.com. The message also says "mailed-by: primary.com" rather than secondary.com and there is no "Signed by" showing.
Can anyone point me in the right direction?
Edit: I have removed the setting which uses the explicit Gmail SMTP server. Now messages are "Signed by" secondary.com as they should be but are still showing as "mailed-by: primary.com".