Receives messages but won't send
This is likely only if you are connected to a POP server. In the Post Office Protocol, the sending and receiving servers are different pieces of software, and often, on different computers.
Work carefully through the steps in Setting Up an Account to ensure that all of your account details are correct. Particularly: check for unwanted spaces at the beginning or end of user IDs, server names, and passwords.
In this case, look hard at the details for Receiving Mail. Note: even though the sending and receiving servers are different, modern ISPs often use the same name for each: for example mail.optusnet.com.au is the name for Optus Australia's sending and receiving servers. Any traffic that arrives on Port 110 is handled by the POP server, traffic on Port 25 is handled by the SMTP server.
Check in the Advanced options to make sure the ports you specify are those you have been told to use by your ISP or System Administrator (and that they are the right way round: usually, the higher-numbered port is for receiving). These ports may be different, particularly for a corporate server, a firewall, or a proxy server. If you have not been told differently, use ports 110 and 25.
If your ISP has failed to set up their system properly, it may be that you are not "logged in" to their server unless you Receive Mail. If you find that you can receive mail, and anything you send immediately afterwards does go, while anything you attempt to send half an hour later doesn't, your ISP may be one of those. You can work around the problem by always checking your mail before attempting to send. If this works, try clicking Advanced options and enabling SMTP server requires authentication.
- Try first with Use same settings as receiving mail server. If you have a local (dialup) connection, this should be all you need.
- If this doesn't work, then specify Log on using.
- You may need to specify the account ID as a fully-qualified name (in other words, your whole email address).