My domain is apitrak.com registered at gandi.net. For my mail I use Apple Mail and th Gendi.net SMTP server throught SSL.
When I respond to a Gmail address, I get an "Undelivered Mail" response by Google, informing me that my email was treated as Spam:
This is the mail system at host relay5-d.mail.gandi.net.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<xxxxxxxxxxxxx@gmail.com>: host
gmail-smtp-in.l.google.com[2a00:1450:400c:c06::1b] said: 550-5.7.1
[2001:4b98:c:538::197 12] Our system has detected that this 550-5.7.1
message is likely unsolicited mail. To reduce the amount of spam sent
550-5.7.1 to Gmail, this message has been blocked. Please visit 550 5.7.1
https://support.google.com/mail/answer/188131 for more information.
9si38384151wmi.71 - gsmtp (in reply to end of DATA command)
Reporting-MTA: dns; relay5-d.mail.gandi.net
X-Postfix-Queue-ID: 2ECF641C09D
X-Postfix-Sender: rfc822; vincent.le@apitrak.com
Arrival-Date: Wed, 13 Jan 2016 12:56:41 +0100 (CET)
Final-Recipient: rfc822; xxxxxxxxxxxxxxx@gmail.com
Original-Recipient: rfc822;xxxxxxxxxxxxxxx@gmail.com
Action: failed
Status: 5.7.1
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 [2001:4b98:c:538::197 12] Our system has
detected that this 550-5.7.1 message is likely unsolicited mail. To reduce
the amount of spam sent 550-5.7.1 to Gmail, this message has been blocked.
Please visit 550 5.7.1 https://support.google.com/mail/answer/188131 for
more information. 9si38384151wmi.71 - gsmtp
Following the link, it tells me to avoid mass mailing: that is absolutely not my case (simple response or fwded response).
It also tells that I should not "change the envelope sender when forwarding email to Gmail." But I don't know what that means.
Any idea?