The document discusses various SMTP errors that can occur when sending emails, including authentication errors, incorrect response codes, permission errors, connection errors, and hostname resolution errors. Potential causes and solutions are provided for each error type.

1. SMTP Errors
Understanding the SMTP errors

2. 2-possible authenticators
Complete error would be like:
Failed to authenticate on SMTP server with username "happykaur1710@gmail.com" using 2 possible authenticators in
.__swiftthirdpartySwiftMailerclassesSwiftMailerTransportEsmtpAuthHandler.php:184
Normal steps that needs to be followed will be:
1. Need to verify credentials
2. If using Gmail, check if Captcha or 2 factor authentication is enabled, So either disable 2-factor authentication or
generate app specific password using:
https://support.google.com/accounts/answer/185833?hl=en

3. Expected response code 250
This SMTP server response simply means everything went well and your message was
delivered to the recipient server. However still there are errors with this code like:
1) Expected response code 250 but got code "530"
Complete error might be like: Expected response code 250 but got code "530", with message "530-5.5.1
Authentication Required. Learn more at 530 5.5.1 https://support.google.com/mail/answer/14257
y15sm42590988pfi.16 - gsmtp " in
.__swiftthirdpartySwiftMailerclassesSwiftMailerTransportAbstractSmtpTransport.php:386

4. Reason for the error:
It comes in case ‘Use SMTP authentication’ is set to ‘No’, and mainly comes when Gmail or MSoffice details
are used for SMTP as they require authentication.
‘Use SMTP authentication’ can be set to ‘No’ works in following case:
If the mail server is used open relay i.e no authentication required. Mainly it is used internal and only some
IPs are allowed to access it. So, in case some users have setup this No, you need not identify that it has to be
set to yes.

5. Client does not have permissions to send as this sender, error message: `550 5.7.1`
Unlike a regular mailbox where you use your own username and password to authenticate to the account,
outbound emails from Kayako will either use the details from an email queue you've defined in Admin CP >
Email Parser > Email Queues - for example support@[yourcompany].com - or the global SMTP details, specified
at Admin CP > Settings > Email.
By default, the email queue address is used as the 'From' address of the sender. And since the email queue is
using its own credentials, the mail server will authenticate those details without a problem.
The error occurs when you try to select a different sender. For example, it commonly occurs when a staff user
selects their own email address in the 'From' dropdown, while updating a ticket.
To resolve the error, you need to configure “Send as” permissions on your mail server so that staff email
accounts can send email using your outbound mailbox account.

6. Uncaught Exception Expected response code 220 but got code "", with message "" in
.__swiftthirdpartySwiftMailerclassesSwiftMailerTransportAbstractSmtpTranspo
rt.php:386
This has not returned any error message along with the response code 220 which means service is
ready.
The exact cause can be checked by going through the logs of the mail server and may arise if incorrect mail
server settings such as port number, mailbox connection type are specified.
It usually gets fixed by updating correct SMTP details, if does not then mail server logs should be checked.

7. Connection could not be established with host smtp.gmail.comm
[php_network_getaddresses: getaddrinfo failed: No such host is known. #0] in
.__swiftthirdpartySwiftMailerclassesSwiftMailerTransportStreamBuffer.php:267
In this error we clearly see that smtp.gmail.com is incorrect, so it should get fixed by correcting host name.
Even if hostname is correct, we might get similar error message due to following:
DNS server not working properly and unable to resolve hostname to its IP.
FIX: Add corresponding IP address as Mailserver hostname.

8. Connection could not be established with host smtp.abc.com
if there is a connection problem or restriction occurs at Firewall (firewall refusing connection silently)
The mentioned hostname is not a mail server or IP Is not whitelisted at mail server, i.e refused from mail
server or firewall
mail server ports mentioned are different than allowed.
Note:
We need to check all of these to whenever there is an error related to hostname and mail server is
not able to resolve address.

9. THANK YOU !