ERROR: {EmailSend} - {api:EmailMicroService} Error occurred while sending the email - wso2

Question

Scenario
I'm sending email via an unsecure smtp server connection with the help of Email connector of wso2.
Connection
<?xml version="1.0" encoding="UTF-8"?>
<localEntry key="unSecureConn" xmlns="http://ws.apache.org/ns/synapse">
<email.init>
<requireAuthentication>true</requireAuthentication>
<connectionType>SMTP</connectionType>
<password>XXXXX</password>
<host>smtp.XXXX.com</host>
<port>25</port>
<name>unSecureConn</name>
<username>XXXXXX</username>
</email.init>
</localEntry>
API:
<?xml version="1.0" encoding="UTF-8"?>
<api context="/email" name="EmailMicroService" port="8290" xmlns="http://ws.apache.org/ns/synapse">
<resource methods="POST" uri-template="/send">
<inSequence>
<log level="full"/>
<email.send configKey="unSecureConn">
<from>{json-eval($.from)}</from>
<to>{json-eval($.to)}</to>
<subject>{json-eval($.subject)}</subject>
<content>{json-eval($.content)}</content>
<contentType>{json-eval($.contentType)}</contentType>
<attachments>{json-eval($.attachments)}</attachments>
</email.send>
<respond/>
</inSequence>
<outSequence/>
<faultSequence/>
</resource>
</api>
Question
I'm facing the relay access denied issue. Although our smtp server is sending emails when logged in to server's user portal. However with the wso2 connector we are facing the following issue:
[2022-11-16 13:55:17,526] ERROR {EmailSend} - {api:EmailMicroService} Error occurred while sending the email with subject hi to ayub.jamal#XXXX.com. org.wso2.carbon.connector.exception.EmailConnectionException: Error occurred while sending the email with subject hi to ayub.jamal#XXXX.com.
at org.wso2.carbon.connector.operations.EmailSend.sendMessage(EmailSend.java:116)
at org.wso2.carbon.connector.operations.EmailSend.connect(EmailSend.java:59)
at org.wso2.carbon.connector.core.AbstractConnector.mediate(AbstractConnector.java:32)
at org.apache.synapse.mediators.ext.ClassMediator.updateInstancePropertiesAndMediate(ClassMediator.java:178)
at org.apache.synapse.mediators.ext.ClassMediator.mediate(ClassMediator.java:97)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:110)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:72)
at org.apache.synapse.mediators.template.TemplateMediator.mediate(TemplateMediator.java:136)
at org.apache.synapse.mediators.template.InvokeMediator.mediate(InvokeMediator.java:170)
at org.apache.synapse.mediators.template.InvokeMediator.mediate(InvokeMediator.java:93)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:110)
at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:72)
at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
at org.apache.synapse.api.Resource.process(Resource.java:342)
at org.apache.synapse.api.API.process(API.java:477)
at org.apache.synapse.api.AbstractApiHandler.apiProcess(AbstractApiHandler.java:93)
at org.apache.synapse.api.AbstractApiHandler.dispatchToAPI(AbstractApiHandler.java:71)
at org.apache.synapse.api.rest.RestRequestHandler.dispatchToAPI(RestRequestHandler.java:90)
at org.apache.synapse.api.rest.RestRequestHandler.process(RestRequestHandler.java:76)
at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:54)
at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:344)
at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:101)
at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:376)
at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:435)
at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:183)
at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: javax.mail.SendFailedException: Invalid Addresses;
nested exception is:
com.sun.mail.smtp.SMTPAddressFailedException: 554 5.7.1 <ayub.jamal#XXXX.com>: Relay access denied
at com.sun.mail.smtp.SMTPTransport.rcptTo(SMTPTransport.java:2079)
at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1301)
at javax.mail.Transport.send0(Transport.java:255)
at javax.mail.Transport.send(Transport.java:124)
at org.wso2.carbon.connector.operations.EmailSend.sendMessage(EmailSend.java:135)
at org.wso2.carbon.connector.operations.EmailSend.sendMessage(EmailSend.java:110)
... 29 more
Caused by: com.sun.mail.smtp.SMTPAddressFailedException: 554 5.7.1 <ayub.jamal#XXXX.com>: Relay access denied
at com.sun.mail.smtp.SMTPTransport.rcptTo(SMTPTransport.java:1979)
... 34 more

Answer 1

Try adding the following parameter to the init.
<requireTLS>false</requireTLS>
Here are all the parameters you can set for the init operation. So depending on your SMTP server, you may have to set the appropriate parameters.
<parameter name="host" description="Host name of the mail server"/>
<parameter name="port" description="The port number of the mail server"/>
<parameter name="name" description="Unique name the connection is identified by"/>
<parameter name="username" description="Username used to connect with the mail server"/>
<parameter name="password" description="Password to connect with the mail server"/>
<parameter name="connectionType" description="Email connection type (protocol) that should be used to establish the connection with the server"/>
<parameter name="readTimeout" description="The socket read timeout value"/>
<parameter name="connectionTimeout" description="The socket connection timeout value"/>
<parameter name="writeTimeout" description="The socket write timeout value"/>
<parameter name="requireTLS" description="Whether the connection should be established using TLS"/>
<parameter name="checkServerIdentity" description="Whether server identity should be checked"/>
<parameter name="trustedHosts" description="Comma separated string of trust host names"/>
<parameter name="sslProtocols" description="Comma separated string of SSL protocol"/>
<parameter name="cipherSuites" description="Comma separated string of Cipher Suites"/>
<parameter name="maxActiveConnections" description="Maximum number of active connections in the pool"/>
<parameter name="maxIdleConnections" description="Maximum number of idle connections in the pool"/>
<parameter name="maxWaitTime" description="Maximum time to wait for a pooled component to become available"/>
<parameter name="minEvictionTime" description="The minimum amount of time an object may sit idle in the pool before it is eligible for eviction"/>
<parameter name="evictionCheckInterval" description="The number of milliseconds between runs of the object evictor"/>
<parameter name="exhaustedAction" description="The behavior of the pool when the pool is exhausted."/>
<parameter name="requireAuthentication" description="Whether authentication is required for SMTP server."/>