The reason is
http://support.google.com/mail/bin/answ ... wer=185812
We have to use gmail email address in certain cases and now we see almost all emails are cut that are sent to gmail it is very very bad for us.
Do you think these recommendations will help in our case:
I am a sender and I don’t want my recipients to see this warning. What should I do?
1 Ensure your emails are authenticated. If you’re sending from a Google Apps account, follow instructions on setting up SPF and DKIM authentication.
2 If you're sending with your Gmail address, but using an account that is outside of Google ('custom from'), use Google's SMTP1 servers to send the mail.
3 If you're sending to a mailing list and seeing the warning, then that mailing list is not using best practices to authenticate their emails and is an easier target for scams. We recommend contacting the admin of your mailing list to set up authentication.