Set every laptop and phone to send on port 587, with the mailbox's username and password and encryption on. Many networks block the old port 25, but authenticated sending on 587 works from anywhere.

Stuck in the outbox

A sales rep at a trade show in Calgary answers a customer's question from the hotel room that evening. The reply sits in the outbox all night, along with two quotes.

New mail arrives without trouble. Back at the office on Monday, everything in the outbox leaves within seconds, as if nothing had been wrong.

The same thing happens some evenings at home. The laptop is fine and so is the mail server; the trouble lies in the network between them.

Receiving and sending are separate

A mail program collects mail and sends it through separate settings, often naming the same server but always using different ports.

So a laptop can receive perfectly and still fail to send. The error messages rarely help, saying only that the server could not be reached or the connection timed out.

When only sending fails, the outgoing settings are the place to look, and the incoming ones can be left alone.

The ports involved

Mail travels through numbered doors on the server, called ports. Four matter here:

Settings written years ago usually point the outgoing server at port 25, with no username or password. At the time, that was normal.

Why networks block port 25

Computers infected with spam software send their junk straight to receiving mail servers on port 25. Blocking that port on customer connections stops them at the source.

Many internet providers now block outgoing port 25 on home connections. Hotels, cafes, trade show halls and some mobile networks do too, or redirect it to their own server, which may refuse the message.

Nothing is wrong with the laptop. It is knocking on a door the network in between has closed, and no setting on the mail server can open it from the other side.

Why it works at the office

The office's business connection usually leaves port 25 open, so the old settings keep working there. Every test anyone ever ran was from the office.

The settings therefore look correct, and in one place they are. They fail only where the rep needs them most: away from the office, answering a customer.

Authenticated sending on the submission port

Port 587 was set aside for people sending their own mail, and it requires the mailbox's username and password before it accepts anything.

Because a login is needed, networks have no reason to block it, and infected computers cannot use it without stolen credentials. The same settings work from the office, a hotel or a kitchen table.

The mail still leaves through your own server, so it passes the checks receiving servers make against your domain, just as mail from the office does.

Turn on encryption for the connection as well. On hotel and trade show Wi-Fi, it keeps the password from travelling in plain text.

A worked example

A CNC machining shop in a Langley industrial park makes small runs of precision parts for equipment makers across Western Canada. Two sales reps visit customers and work trade shows.

Both reps' laptops and phones had been set up from an old instruction sheet: outgoing server on port 25, no login. At the office, every message went out.

At a trade show in Edmonton, quotes sat in the outbox for two days, and the rep noticed only when a customer phoned to ask where they were.

Every laptop and phone now sends on port 587, with the mailbox's own username and password and encryption switched on. The instruction sheet was rewritten with the new settings.

Each device was tested before the next trip from a phone's hotspot, away from the office network, so the test matched the road rather than the office.

The settings work the same from the shop, a hotel or home, because networks leave that port open and the login proves who is sending.

What to change on each laptop

In the mail program's account settings, find the outgoing server. Keep the server name your host gives, set the port to 587 and choose TLS encryption, or SSL on 465 if your host names it.

Then tick the option saying the outgoing server requires authentication, using the same username and password as for incoming mail. In Outlook these sit under More Settings, on the Outgoing Server and Advanced tabs.

If your host's own instructions differ, follow them; some hosts use a separate name for the outgoing server.

And on each phone

Phones keep their own copy of the settings, set up separately. On an iPhone they sit under the account's outgoing mail server; on Android, under the account's outgoing settings.

Make the same four changes: the server name, port 587, encryption on and a login. Then send a test message while connected to something other than the office Wi-Fi.

Tablets used for email need the same treatment. So does any home computer from which staff send company mail in the evening.

The counter-case

Staff who never leave the office, or who only use webmail when travelling, may never meet this problem. Their old settings will go on working where they are.

But any laptop or phone that might travel should be changed now, while it is in the office and easy to test. Unauthenticated sending on port 25 is a setting worth retiring anyway.

Mail sent through webmail never touches these settings at all, which is why webmail often works on the road when the laptop's mail program does not.

Settings that work on the road

  1. List every laptop and phone that sends company mail.
  2. Check the outgoing port on each one.
  3. Change it to 587, or 465 if your host says so.
  4. Turn on encryption for the outgoing connection.
  5. Tick outgoing authentication with the mailbox's own login.
  6. Test from a phone's hotspot, not the office network.
  7. Rewrite the setup sheet so new devices start right.

Step six is the one that proves it. A test from the office passes whether the settings are right or not; only a test from another network shows what the road will do.

Another login worth protecting before the next trip, the one that runs a business's Facebook Page, is covered in messages saying your Facebook page will be shut down.

Frequently asked questions

Why does email send from the office but not from a hotel?

Many networks block port 25, the old mail port, to stop infected computers sending spam. Settings copied years ago often still use it, and the office connection happens to allow it.

Why can I still receive mail?

Receiving and sending use different servers and ports. Collecting mail is rarely blocked, so the inbox fills normally while outgoing messages wait in the outbox.

What is port 587?

The submission port, meant for people sending their own mail with a username and password. Networks leave it open because it cannot be used without a login.

What settings should each device use?

The outgoing server your host gives you, port 587, encryption switched on, and authentication with the same username and password as the mailbox itself.

What about port 465?

It is an older encrypted port that many hosts still offer for the same purpose. Use it when your host's instructions name it, with SSL switched on.

Do phones need the same change?

Yes. Phones send through hotel Wi-Fi and mobile networks, which may block port 25 too. Each phone's outgoing server settings need the same four changes.

West Coast Media Solutions Inc. provides web design, web development, hosting, digital marketing, and business consulting to organisations across Canada, drawing on more than twenty-five years in the field.

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