One of the common issues people face when sending emails is the wrong mail client configuration problem. To check whether the problem is with the settings of your email client, you must try to send a message through webmail.
These clients are previously configured to connect with the SMTP service on the host server. If you are able to send an email using webmail successfully, then that means there is some issue with the configuration of the email client.
You can find the right mail settings and resolve the problem by going to Site Toos, Email, and Accounts. Then, you need to select the email account, choose the Kebab menu, and finally select Mail Configuration.
There are two cases where your email won't be sent and the receiving host will reject it. In such a case, your message will come back to the mailbox.
Some of the main reasons for rejection are stated below.
In case you are sure that you have entered the right password even then you must check once again. In case you are thinking that it cannot be wrong because you copied and pasted it, then you may get surprised.
A lot of time Firefox and various other applications some extra space gets inserted while pasting the password. When that happens, one blank space gets added to the end of your password. Therefore, it is always advisable to copy and paste the password.
A lot of email providers need to use a secure connection for connecting to SMTP. You need to ensure that this option is selected in the email client you are using. In Outlook, you will always see the option, "This server needs a secure connection". Some servers may need to connect to port 465 or port 25. In case none of the ports are working, then you can always try port 587.
Press the Windows and R keys simultaneously in the cmd and then open the command prompt box. After that, you need to type telnet domaiin.com. You can also replace the domain name with the actual domain name.
In case you see a message that has 220 or "Connected" in it, then it will open and you will be ready to use it. In case you receive the error that says couldn't connect or no response, then that means it has been blocked. Hold Ctrl + } and then press the enter key for ending telnet connection.