iPhone: The Missing Manual

Can't Send Email

It's happened to thousands of people. You set up your POP email account (Setting Up Your Account), and everything looks good. But although you can receive mail, you can't send it. You create an outgoing message, you tap Send. The whirlygig "I'm thinking" cursor spins and spins, but the iPhone never sends the message.

The problem's cause is very technical, but here's a nicely oversimplified explanation.

When you send a piece of postal mail, you might drop it off at the post office. It's then sent over to the addressee's post office in another town, and delivered from there.

In a high-tech sort of way, the same thing happens with email. When you send a message, it goes first to your Internet provider's email server (central mail computer). It's then sent to the addressee's mail server, and the addressee's email program picks it up from there.

But spammers and spyware writers became an increasing nuisance, especially people who wrote zombies—spyware on your computer that churns out spam without your knowledge. So the big ISPs (Internet service providers) began fighting back in two ways—both of which can block outgoing mail from your iPhone, too. Here's the scoop:

• Use port 587.Ports are invisible "channels" from a computer to the Internet. One conducts email, one conducts Web activity, and so on. Most computers send email out on port 25.

  In an effort to block zombie spam, though, the big ISPs have rigged their networks so that mail you send from port 25 can go only to one ...