What's Causing This Error
There are multiple reasons for this error. Most of the time, it is related to connectivity issues between the client and the email server.
Here are some of the most common issues that can cause this error:
- SMTP restrictions on the email server.
- Firewall restrictions.
- Incorrect settings on the mail client.
- DNS failures.
Solution - Here's How To Resolve It
To resolve this issue, you must go through each of the following troubleshooting steps:
- Ensure that the email server does not have any restrictions that may prevent a client from connecting to the server.
- Ensure that the email client has the necessary connectivity via the recommended ports.
- Ensure that all the settings on the mail client are correct.
- Ensure the client can resolve the email server's DNS records using the configured DNS server.