[TriLUG] mails from list are coming with warning on gmail

[Tapas Mishra]

All the mails coming from Ubuntu users mailing list  are
coming to my mail box with a warning from gmail.
The warning is

"This message may not have been sent by: user at gmail.com  Learn more
Report phishing "


Where the address user at gmail.com is some one who posted question to the list.
What can be wrong? I am interested to understand this problem from
technical end.
 It is across all *@lists.ubuntu.com what can be a quick fix for the same?

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Tapas