If you are able to receive emails but not send email, this usually indicates that your internet service provider is blocking your connection from using anyone elses outgoing mail servers but their own. Many internet service providers (ISPs) block using 3rd party SMTP for outgoing emails to prevent their connection from being used for spamming. To work around this, there is an alternative port open Port 26. Change your outgoing mail server (SMTP) from port 25 to port 26.
If using Outlook, please enable "Outgoing SMTP Server Requires Authentication".
Some ISPs that block port 25 include:
- People PC
- Comcast ATTBI
What if my ISP is blocking port 25 and port 26?
Sometimes ISPs block ports 25 and 26 and you will have to follow your ISP's outlined procedures for sending an emails. You can also try contacting your ISP to request for them to open port 25 for you. Some ISPs will require you to use their SMTP servers for outgoing emails so that they can monitor outgoing email on their network for spam.
You need to get in touch with your ISP about their SMTP servers information for outgoing email. You can usually find this information on the knowledgebase of the ISP's website.
You will still be able to send emails from your domain (e.g. firstname.lastname@example.org); it just has to be sent through your ISPs SMTP servers.
WireNine SMTP server requires authentication.