smtp server setup

Hello! I installed a new instance of xwiki on my local machine. I tried to set up the email notification but it didn't really work. In the XWiki Preferences I set the outgoing smtp server to several smtp servers such as smtp.google.com, smtp.comcast.net, etc. Howver, there seem to be some authentication issues and I get the following error message: *** Error number 4001 in 4: Error while parsing velocity page Demo.SendMailTestPage Wrapped Exception: Invocation of method 'sendMessage' in class com.xpn.xwiki.XWiki threw exception class com.xpn.xwiki.XWikiException : Error number 10006 in 10: Could not send mail to server smtp.comcast.net port 25 error code 530 (530 Authentication required ) OR Error number 4001 in 4: Error while parsing velocity page Demo.SendMailTestPage Wrapped Exception: Invocation of method 'sendMessage' in class com.xpn.xwiki.XWiki threw exception class com.xpn.xwiki.XWikiException : Error number 10006 in 10: Could not send mail to server smtp.gmail.com port 25 error code 530 (530 5.7.0 Must issue a STARTTLS command first h14sm757315wxd ) *** I also tried to use my own smtp server (hmailserver) but then I had some relay problems and the following error message: *** Error number 4001 in 4: Error while parsing velocity page Demo.SendMailTestPage Wrapped Exception: Invocation of method 'sendMessage' in class com.xpn.xwiki.XWiki threw exception class com.xpn.xwiki.XWikiException : Error number 10006 in 10: Could not send mail to server mail.hmailserver.com port 25 error code 550 (550-207-105-15-139.ded.pacbell.net (XWiki version 0.9.840) 207.105.15.139? is 550-currently not permitted to relay through this server. Perhaps you have not 550-logged into the pop/imap server in the last 30 minutes or do not have SMTP 550 Authentication turned on in your email client. ) *** I have right now no idea how to resolve these issues. I would appreciate any help in setting up the smtp server for the email notification. Cheers, Jens