Hi Khalid,
I think that your new app is deployed in the Cloud v4, and there is doesn't support the smtp server localhost:25 as it is in the Cloud v3.
Mendix Mail Servers
The Mendix mail servers are only available in Mendix Cloud v3. If you are using Mendix Cloud v3 and are sending more than 1000 messages per day we recommend you use an external mail service as described above.
You can read more about it at: https://docs.mendix.com/howtogeneral/mendixcloud/sending-email.
Good luck.
Edit: In v4 it is not possible to send mail over port 25 because this port is blocked by Mendix:
Please note that sending email from Mendix Cloud v4 can not happen over port 25, as this port is blocked in our infrastructure.
Hi Khalid
Did you get solution for this issue I am also facing same error "Sending the email to the following server failed : pop.gmail.com:465 at Experiments.ACT_DownloadPDFFile_2 (JavaAction : 'Send email')"
I am getting this error in the localhost but when i test in the cloud with same email configuration that time is working fine
com.mendix.systemwideinterfaces.MendixRuntimeException: org.apache.commons.mail.EmailException: Sending the email to the following server failed : smtpout.secureserver.net:465 at EmailTemplate.SendEmailMessage (JavaAction : 'Send Email') at EmailTemplate.IVK_SendTestMessage (SubMicroflow : 'SendEmailMessage') Advanced stacktrace: at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: com.mendix.systemwideinterfaces.MendixRuntimeException: org.apache.commons.mail.EmailException: Sending the email to the following server failed : smtpout.secureserver.net:465 at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: org.apache.commons.mail.EmailException: Sending the email to the following server failed : smtpout.secureserver.net:465 at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: Sending the email to the following server failed : smtpout.secureserver.net:465 at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: Could not connect to SMTP host: smtpout.secureserver.net, port: 465 at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83) Caused by: unable to find valid certification path to requested target at com.mendix.modules.microflowengine.MicroflowUtil.processException(MicroflowUtil.java:83)