It was brought to my attention that emails sent due to an enabled Auto Response setting (used for automating OOF replies) were going into Gmail's Spam folder. These were set up using the MailEnable Web interface. Emails sent directly to a Gmail address correctly appeared in the inbox--same account. After duplicating this issue using my account, I looked at the header of both a successful email and an unsuccessful email. Turns out that the email sent from the auto responder failed DKIM and therefore was put into the spam folder. I'm not sure how MailEnable is sending these auto response emails.
Below is an SMTP header relating to DKIM from an email sent manually to a Gmail address:
dkim=pass email@example.com header.s=MESelector header.b=fnSFFnB+;
spf=pass (google.com: domain of firstname.lastname@example.org designates 18.104.22.168 as permitted sender) email@example.com;
dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=lno.io
dkim-signature: v=1; c=relaxed/relaxed; h=from:to:subject:date:message-id:mime-version:content-type:reply-to; d=lno.io; s=MESelector; a=rsa-sha1; bh=[redacted]
and here is the same section on an auto response email that fails DKIM:
dkim=neutral (body hash did not verify) firstname.lastname@example.org header.s=MESelector header.b=MRGp5RES;
spf=pass (google.com: best guess record for domain of email@example.com designates 22.214.171.124 as permitted sender) smtp.helo=smtpout.learnnowonline.com;
dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=lno.io
dkim-signature: v=1; c=relaxed/relaxed; h=to:date:message-id:content-type:content-transfer-encoding:from:subject:reply-to; d=lno.io; s=MESelector; a=rsa-sha1; bh=[redacted]
Both of these emails should be coming from the same server with the same IP address. Is there a place to configure how auto responses behave?