When I send an email with the PHP Swift mailer to this server: smtp.exchange.example.com like this:
// Load transport
$this->transport =
Swift_SmtpTra
This might be old but somebody might get help through this. I too faced the same problem and received a mail on my gmail account stating that someone is trying to hack your account through an email client or a different site. THen I searched and found that doing below would resolve this issue.
Go to https://accounts.google.com/UnlockCaptcha and unlock your account for access through other media/sites.
UPDATE : 2015
Also, you can try this, Go to https://myaccount.google.com/security#connectedapps At the bottom, towards right there is an option "Allow less secure apps". If it is "OFF", turn it on by sliding the button.