Issue connecting to Gmail when using mailR package to send email - r

Question

I am trying to send mail from R through gmail using the mailR package. I was able to use it using the unsecure host and port 25, but it gets sorted to spam (which obviously isn't super desirable). I have enable allowing less secure apps to send through gmail, and then I tried to send to smtp, using the following code:
send.mail(from = "themattbetz#gmail.com",
to = "themattbetz#gmail.com",
subject = "Test Subject",
body = "Test body of the email",
smtp = list(host.name = "smtp.gmail.com",port = 465,
user.name = "themattbetz#gmail.com",
passwd = "******",
ssl=TRUE),
authenticate = TRUE,
send = TRUE)
And got this following error message:
org.apache.commons.mail.EmailException: Sending the email to the following server failed : smtp.gmail.com:465
at org.apache.commons.mail.Email.sendMimeMessage(Email.java:1410)
at org.apache.commons.mail.Email.send(Email.java:1437)
at sun.reflect.GeneratedMethodAccessor7.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at RJavaTools.invokeMethod(RJavaTools.java:386)
Caused by: javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 465;
nested exception is:
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2055)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:697)
at javax.mail.Service.connect(Service.java:386)
at javax.mail.Service.connect(Service.java:245)
at javax.mail.Service.connect(Service.java:194)
at javax.mail.Transport.send0(Transport.java:253)
at javax.mail.Transport.send(Transport.java:124)
at org.apache.commons.mail.Email.sendMimeMessage(Email.java:1400)
... 5 more
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.ssl.Alerts.getSSLException(Unknown Source)
at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
at sun.security.ssl.Handshaker.processLoop(Unknown Source)
at sun.security.ssl.Handshaker.process_record(Unknown Source)NULL
at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at com.sun.mail.util.SocketFetcher.configureSSLSocket(SocketFetcher.java:543)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:348)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:215)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2019)
... 12 more
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.validator.PKIXValidator.doBuild(Unknown Source)
at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
... 24 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source)
at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
at java.security.cert.CertPathBuilder.build(Unknown Source)
... 30 more
Error: EmailException (Java): Sending the email to the following server failed : smtp.gmail.com:465
In looking through previous questions, I found another user had the exact same problem, but that by enabling less secure programs through gmail, they were able to resolve it. For some reason, even with this enabled, it won't work for me. Any suggestions?
I also intend on using it send attachments once I get over this hurdle.
Note: I'm not very knowledgeable of java or html.