Email client protocols and port numbers

The port numbers you set determine the protocol your email client uses. There are four basic options. IMAP secure is the recommended configuration:

  • IMAP (insecure)
  • IMAP (secure)
  • POP3 (insecure)
  • POP3 (secure)

Below are the settings you can use for each protocol along with the security settings.

Incoming

  • IMAP | Port 143 (Insecure Transport — No SSL function enabled)
  • IMAP | Port 993 (Secure Transport   — SSL function enabled)
  • POP3 | Port 110 (Insecure Transport — No SSL function enabled)
  • POP3 | Port 995 (Secure Transport   — SSL function enabled)

Outgoing

  • SMTP | Port 587 (Insecure Transport — No SSL function enabled)
  • SMTP | Port 465 (Secure Transport   — SSL function enabled)
  • SMTP | Port 25 (username/password authentication MUST also be enabled!)

Port 587 is a highly recommended alternative port because port 25 is often blocked by ISPs.

SMTP

See also: SMTP on Wikipedia, SMTP quota

  • Simple Mail Transfer Protocol (SMTP) is the de facto standard for outgoing email transmissions across the Internet.
  • SMTP is a relatively simple, text-based protocol, where one or more recipients of a message are specified (and in most cases verified to exist) and then the message text is transferred.
  • It is a client-server protocol, where the client transmits an email message to the server.

POP3 vs IMAP

POP3 and IMAP are two different ways of checking mail. A mail client program connects to the mail server using either POP3 or IMAP. All DreamHost mail accounts support both POP3 and IMAP connections automatically.

What is POP3?

POP3 downloads all mail from the server from the Inbox and stores it on your computer. The emails are removed from the server and only stored locally in your mail client program. Emails are available when you're not connected to the Internet.

The POP setup will only download mail from the Inbox folder. Any other emails in folders or sub-folders (such as Trash, Draft, and Sent) must be moved to the Inbox in order for that to be viewed or downloaded via POP.

What is IMAP?

IMAP syncs your mail client program with the server. Emails stay on the server, and you can make and view mail folders on the server in addition to the Inbox. Most mail client program have a feature to initially sync just the email headers, so you can quickly see what emails you have, then download the message body when you want to read the email. Since emails stay on the server, you can see all your emails from any mail client program or device. Webmail uses IMAP.

IMAP is the preferred protocol for accessing your mail from various locations as well as through multiple devices. For example, having your email address set up on your home computer, a tablet, and a phone, IMAP centralizes the storage of your emails to your DreamHost mail server; as long as you have an Internet connection, you can connect to your IMAP servers to access your mail from anywhere on any device.

Which should I choose?

IMAP is recommended since email is available from any device you choose to connect with. POP downloads the emails to a specific device so it's possible email could be lost or misplaced.

Use IMAP if you want to check email from multiple computers or devices. Use POP3 if you want your email always accessible, even when there's no Internet connection. But, be aware that email will only be available on the device to which you downloaded them.

If you have been using IMAP and have some mail stored in folders other than the Inbox, move the emails to the Inbox before using POP3.

Example setup using a secure IMAP connection

Secure IMAP incoming configuration

IMAP secure.fw.png
  • This example shows the ‘contact@example.com’ user being set up as an IMAP user with SSL enabled using Port 993 for incoming mail.
  • The server name being used is ‘sub4.mail.dreamhost.com’ with ‘Authentication’ set to ‘Normal password’. Make sure to only use your mail cluster name.

Secure outgoing settings

IMAP outgoing.fw.png
  • This setup shows the SMTP settings with SSL enabled for the ‘contact@example.com’ email address.
  • The user is set to use Port 465 with SSL for secure connections and the ‘Authentication’ is set here as ‘Normal password’.
  • The port setting and the SSL option must match each other – i.e., if you’re using SSL/TLS you must use secure ports.
  • Enabling SSL (Secure Transport) will require an additional step in confirming and accepting the certificate for the secure connection for both incoming and outgoing mail.
  • It's normal to get a certificate warning when attempting to connect using a secure connection. View the Certificate Domain Mismatch Error article for solutions.

See also

Did this article answer your questions?

Article last updated .