Once I had this weird problem with setting up a Gmail account in Prestashop for a friend. I could not send anything from his account. Thinking that it might be something to do with a firewall I did a simple manual smtp test on smtp.gmail.com.
1. First we will need to encode your user name and password using Base64.
2. Login to your server and in ssh
perl -MMIME::Base64 -e 'print encode_base64("\000youremail\@.gmail.com\000yourpassword")'
Which will return the encoded string like this:
AHRlc3RAY2VyZXphc3ZlcmRlcy5jb20AdGVzdCExFjM=
3. Use openssl to establish the connection
openssl s_client -connect smtp.gmail.com:465 -crlf -ign_eof
4. Greet the server 
EHLO localhost
5. Authenticate
AUTH PLAIN AHRlc3RAY2VyZXphc3ZlcmRlcy5jb20AdGVzdCExFjM=
6. Send a test email
MAIL FROM: RCPT TO: DATA Subject: Test Oppan gangnam style! .
That’s all. My problem with Prestashop was resolved in the end. It was a bug in Prestashop. Here is the link for anyone interested: http://forge.prestashop.com/browse/PSCFV-5838
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