The email client shows the content of the mailbox on the server and applies each of your actions there: read, unread, filed, deleted. All your devices see the same state of the mailbox, with all its folders (sent, drafts, junk, folders you created). Most email clients also keep a copy of the messages on the device for offline reading; changes made offline are applied to the server when you reconnect. IMAP is not a backup: since everything is synchronized, a message deleted on one device is also deleted on the server and on all your other devices. Since messages stay on the server, they count towards the mailbox quota. A full mailbox no longer receives new emails.

The email client downloads new messages from the inbox to the device. Depending on its settings, it then deletes them from the server or leaves a copy there. Only the inbox is downloaded: the other folders on the server, including junk, are not. Actions taken in the email client (read, filed, deleted) stay on that device. If you check the same mailbox from another device or from webmail, you will not find that state there. Once deleted from the server, the messages only exist on that device: if it is lost or damaged without a backup, they are lost.

SMTP (Simple Mail Transfer Protocol) is the protocol that carries emails. Your email client uses it to hand the messages you send over to our server, then servers use it between themselves to pass them on to the recipient's server. It is also through SMTP that emails addressed to you arrive on our server. For you, in your email client, the rule is simple: SMTP to send, IMAP or POP to receive. For sending, set up in your email client: the outgoing server mail01.swisscenter.com (or the name shown in your console); port 465 with SSL/TLS, recommended; if your email client or network does not accept it, port 587 with STARTTLS; authentication enabled, with your full email address as the username and the mailbox password. Sending to external recipients can be disabled for an address, with the Sending mail (SMTP) switch in its Services tab. An address whose sending is disabled still receives its emails.

Choose between IMAP and POP, and understand the role of SMTP

Q: Which one to choose?

Choose IMAP in most cases, especially if: you check the same mailbox from several devices (computer, phone, webmail); you want to find the same mailbox state and the same folders everywhere; you want your messages to stay on the server if a device is lost. POP may be suitable if you collect your mail from a single device, and if you prefer messages to leave the server once collected, for example so as not to fill up the mailbox quota. In that case, remember to back up that device. You can allow or disable POP and IMAP separately for each address, in the address's Services tab in the Apanel console (see Manage the services of an e-mail address).

To use your email address in an email client (Outlook, Thunderbird, the app on your phone), three protocols come into play. Two are used to receive your emails, that is, to read them from our server: IMAP and POP. The third, SMTP, is used to send them. When you set up your email client, you choose between IMAP and POP for receiving; sending always goes through SMTP.

This article explains the role of each one and helps you choose between IMAP and POP. The values to enter in your email client are detailed in Email settings for all email clients (IMAP, POP, SMTP).

In short

Protocol	What it is for	Port at SwissCenter	Security
IMAP	Receiving: reading and synchronizing your emails, which stay on the server	`993`	SSL/TLS
POP (POP3)	Receiving: downloading your emails to a device	`995`	SSL/TLS
SMTP	Sending your emails	`465` (recommended), alternative: `587`	SSL/TLS on 465, STARTTLS on 587

The server is the same for all three: mail01.swisscenter.com. The exact name of your domain's server is shown in the Apanel console: in Hosting management, Misc informations box, line E-mail SSL server name (POP3S / IMAPS / SMTPS). If a different name appears there, use the one from the console.

How does IMAP work?

The email client shows the content of the mailbox on the server and applies each of your actions there: read, unread, filed, deleted.
All your devices see the same state of the mailbox, with all its folders (sent, drafts, junk, folders you created).
Most email clients also keep a copy of the messages on the device for offline reading; changes made offline are applied to the server when you reconnect.
IMAP is not a backup: since everything is synchronized, a message deleted on one device is also deleted on the server and on all your other devices.
Since messages stay on the server, they count towards the mailbox quota. A full mailbox no longer receives new emails.

How does POP work?

The email client downloads new messages from the inbox to the device. Depending on its settings, it then deletes them from the server or leaves a copy there.
Only the inbox is downloaded: the other folders on the server, including junk, are not.
Actions taken in the email client (read, filed, deleted) stay on that device. If you check the same mailbox from another device or from webmail, you will not find that state there.
Once deleted from the server, the messages only exist on that device: if it is lost or damaged without a backup, they are lost.

Which one to choose?

Choose IMAP in most cases, especially if:

you check the same mailbox from several devices (computer, phone, webmail);
you want to find the same mailbox state and the same folders everywhere;
you want your messages to stay on the server if a device is lost.

POP may be suitable if you collect your mail from a single device, and if you prefer messages to leave the server once collected, for example so as not to fill up the mailbox quota. In that case, remember to back up that device.

You can allow or disable POP and IMAP separately for each address, in the address's Services tab in the Apanel console (see Manage the services of an e-mail address).

What is SMTP for?

SMTP (Simple Mail Transfer Protocol) is the protocol that carries emails. Your email client uses it to hand the messages you send over to our server, then servers use it between themselves to pass them on to the recipient's server. It is also through SMTP that emails addressed to you arrive on our server. For you, in your email client, the rule is simple: SMTP to send, IMAP or POP to receive.

For sending, set up in your email client:

the outgoing server mail01.swisscenter.com (or the name shown in your console);
port 465 with SSL/TLS, recommended; if your email client or network does not accept it, port 587 with STARTTLS;
authentication enabled, with your full email address as the username and the mailbox password.

Sending to external recipients can be disabled for an address, with the Sending mail (SMTP) switch in its Services tab. An address whose sending is disabled still receives its emails.

Going further

Email settings for all email clients (IMAP, POP, SMTP): the values to enter and the steps for each email client.
Mailbox full: increase the quota of an e-mail address: with IMAP, messages stay on the server and fill up the mailbox.
Manage the services of an e-mail address (webmail, POP, IMAP, SMTP, WebDAV): allow or disable POP, IMAP and sending for an address.