Add this lines of code in your portal-ext.properties
mail.session.mail.pop3.host=pop.gmail.com
mail.session.mail.pop3.password=PASSWORD
mail.session.mail.pop3.port=110
mail.session.mail.pop3.user=USER
mail.session.mail.imap.host=imap.gmail.com
mail.session.mail.imap.port=993
mail.session.mail.store.protocol=imap
mail.session.mail.transport.protocol=smtp
mail.session.mail.smtp.host=smtp.gmail.com
mail.session.mail.smtp.password=PASSWD
mail.session.mail.smtp.user=USERID@gmail.com
mail.session.mail.smtp.port=465
mail.session.mail.smtp.auth=true
mail.session.mail.smtp.starttls.enable=true
mail.session.mail.smtp.socketFactory.class=javax.net.ssl.SSLSocketFactory
* Please user your password in place of PASSWD and your gmail user id in place of USERID.
By three different ways we can configure mail server in Liferay. I am using Liferay 6.2 and initially I got an error that could not connect to smtp host localhost port 25 in liferay by using different code. So I used above code and my mail server is configured properly and my application is able to send mail to the user in forgot password case.
And please see this link. This link help me to solve the issue.
https://www.permeance.com.au/web/tim.telcik/home/-/blogs/how-do-i-configure-liferay-portal-to-use-google-mail
Thanks
asif aftab