Due to SPAM restrictions the free accounts do not allow anymore to send emails in behalf of
gmail.com.
For example: If you registered your account with an email
HOTEL...@gmail.com and you try to send emails from a free account the email server will identify has SPAM and refuse.
To continue using this feature you need to change your email to something such hotel@HOTEL_NAME.com
The other alternative is to switch to a paid account. Nevertheless the paid accounts have limit number of emails per day (at the present the max. is 50 per day)
WS