I am using gmail as SMTP server (via ssmtp mail transfer agent in Ubuntu 12.04) for sending outgoing mails from my server. But the problem is that Google often blocks authentication attempts by my machine. Sometimes it works without problems but sometimes it gives this message :
Authorization failed (534 5.7.9 https://support.google.com/mail/bin/answer.py?answer=78754 kn10sm96120374oeb.0 - gsmtp)
How could fix this issue permanently ? I created a separate account that is meant to be used only for sending mails by this machine.