For @custom-domain.ext mailbox format go here:
Aruba.it custom domains IMAP, POP3, SMTP settings

POP3

Server: pop3.aruba.it
SSL: true-implicit
Port: 995 (default)
User :  email address (e.g.: name@aruba.it or name@technet.en)

using (Pop3 client = new Pop3())
{
    client.ConnectSSL("pop3.aruba.it");
    client.UseBestLogin("user@aruba.it", "password");

    // ...

    client.Close();
}

IMAP

Server:  imap.aruba.it
SSL: true-implicit
Port: 993 (default)
User: email address (e.g.: name@aruba.it or name@technet.en)

using (Imap client = new Imap())
{
    client.ConnectSSL("imap.aruba.it");
    client.UseBestLogin("user@aruba.it", "password");

    // ...

    client.Close();
}

SMTP

Server:  smtp.aruba.it
SSL: true-implicit
Port:  465 (default)
User: email address (e.g.: name@aruba.it or name@technet.en)

using (Smtp client = new Smtp())
{
    client.ConnectSSL("smtp.aruba.it");
    client.UseBestLogin("user@aruba.it", "password");

    // ...

    client.Close();
}

For @aruba.it and @technet.it mailbox formats go here:
@aruba.it and @technet.it IMAP, POP3, SMTP settings

POP3

Server: pop3s.aruba.it
SSL: true-implicit
Port: 995 (default)
User :  email address (e.g.: name@aruba.it or name@technet.en)

using (Pop3 client = new Pop3())
{
    client.ConnectSSL("pop3s.aruba.it");
    client.UseBestLogin("user@custom-domain.ext", "password");

    // ...

    client.Close();
}

IMAP

Server:  imaps.aruba.it
SSL: true-implicit
Port: 993 (default)
User: email address (e.g.: name@aruba.it or name@technet.en)

using (Imap client = new Imap())
{
    client.ConnectSSL("imaps.aruba.it");
    client.UseBestLogin("user@custom-domain.ext", "password");

    // ...

    client.Close();
}

SMTP

Server:  smtps.aruba.it
SSL: true-implicit
Port:  465 (default)
User: email address (e.g.: name@aruba.it or name@technet.en)

using (Smtp client = new Smtp())
{
    client.ConnectSSL("smtps.aruba.it");
    client.UseBestLogin("user@custom-domain.ext", "password");

    // ...

    client.Close();
}

Outlook365 supports access via IMAP, POP3 and SMTP protocols. Below you can find the configuration settings for all protocols.

Latest Office 365 version

For latest Office 365 after the service upgrade, use the following settings:

IMAP

Server: outlook.office365.com
SSL: true-implicit, true-explicit (StartTLS)
Port: 993 (default), 143 (default)
User: pat@domain.onmicrosoft.com or pat@your-domain.com

POP3

Server: outlook.office365.com
SSL: true-implicit, true-explicit (StartTLS)
Port: 995 (default), 110 (default)
User: pat@domain.onmicrosoft.com or pat@your-domain.com

SMTP

Server: smtp.office365.com
SSL: true-explicit (StartTLS)
Port: 587(default)
User: pat@domain.onmicrosoft.com or pat@your-domain.com

IMAP and POP3 servers allow both: implicit/TLS SSL and explicit SSL/TLS, so you can ConnectSSL method -or- Connect and StartTLS.

SMTP server requires explicit SSL – use Connect and StartTLS method.

// C#

using (Imap client = new Imap())
{
    client.ConnectSSL("outlook.office365.com");
    client.UseBestLogin("user@domain.onmicrosoft.com", "password");
    ...
}

using (Pop3 client = new Pop3())
{
    client.ConnectSSL("outlook.office365.com");
    client.UseBestLogin("user@domain.onmicrosoft.com", "password");
    ...
}

using (Smtp client = new Smtp ())
{
    client.Connect("smtp.office365.com");
    client.StartTLS();

    client.UseBestLogin("user@domain.onmicrosoft.com", "password");
    ...
}

' VB.NET

Using client As New Imap()
	client.ConnectSSL("outlook.office365.com")
	client.UseBestLogin("user@domain.onmicrosoft.com", "password")
	...
End Using

Using client As New Pop3()
	client.ConnectSSL("outlook.office365.com")		
	client.UseBestLogin("user@domain.onmicrosoft.com", "password")
	...
End Using

Using client As New Smtp()
	client.Connect("smtp.office365.com")
	client.StartTLS()

	client.UseBestLogin("user@domain.onmicrosoft.com", "password")
	...
End Using

Office 365 pre-upgrade

For latest Office 365 pre-upgrade, use the following settings:

On the main screen go to “Options” / “See All Options…”:

Now click the “Settings for POP, IMAP, and SMTP access…” link:

You can find POP, SMTP and IMAP server addresses and settings on the popup window:

Office365 uses default ports for IMAP, POP3 and SMTP protocols. That means that you don’t need to remember port numbers, as Mail.dll .NET email component is going to use correct port numbers by default.

IMAP

Server: podXXXX.outlook.com
SSL: true-implicit
Port: 993 (default)
User: pat@domain.onmicrosoft.com or pat@your-domain.com

POP3

Server: podXXXX.outlook.com
SSL: true-implicit
Port: 995 (default)
User: pat@domain.onmicrosoft.com or pat@your-domain.com

SMTP

Server: podXXXX.outlook.com
SSL: true-explicit
Port: 587 (default)
User: pat@domain.onmicrosoft.com or pat@your-domain.com

IMAP and POP3 servers use implicit SSL – use ConnectSSL method. SMTP server requires explicit SSL – use Connect and StartTLS method.

// C#

using (Imap client = new Imap())
{
    client.ConnectSSL("podXXXX.outlook.com");
    client.UseBestLogin("user@domain.onmicrosoft.com", "password");
    ...
}

using (Pop3 client = new Pop3())
{
    client.ConnectSSL("podXXXX.outlook.com");
    client.UseBestLogin("user@domain.onmicrosoft.com", "password");
    ...
}

using (Smtp client = new Smtp ())
{
    client.Connect("podXXXX.outlook.com");
    client.StartTLS();

    client.UseBestLogin("user@domain.onmicrosoft.com", "password");
    ...
}

' VB.NET

Using client As New Imap()
	client.ConnectSSL("podXXXX.outlook.com")
	client.UseBestLogin("user@domain.onmicrosoft.com", "password")
	...
End Using

Using client As New Pop3()
	client.ConnectSSL("podXXXX.outlook.com")		
	client.UseBestLogin("user@domain.onmicrosoft.com", "password")
	...
End Using

Using client As New Smtp()
	client.Connect("podXXXX.outlook.com")
	client.StartTLS()

	client.UseBestLogin("user@domain.onmicrosoft.com", "password")
	...
End Using

You can find more details about using implicit and explicit SSL or TLS with email protocols:

• Using SSL with IMAP
• Using SSL with POP3
• Using SSL with SMTP

iCloud supports access via IMAP and SMTP protocols, POP3 is not supported. Below you can find the configuration settings for those protocols.

Both (IMAP and SMTP) use implicit SSL (use ConnectSSL method) and explicit SSL (you can use Connect method and then secure the channel using StartTLS method)

IMAP

Server: imap.mail.me.com
SSL: true-implicit
Port: 993 (default)
User: pat (not pat@icloud.com)

SMTP

Server: smtp.mail.me.com
SSL: true-explicit
Port: 587 (default)
User: pat@icloud.com (not pat)

Following are the code samples for Mail.dll .NET IMAP, POP3 and SMTP component.

// C#

using (Imap client = new Imap())
{
    client.ConnectSSL("imap.mail.me.com");
    client.UseBestLogin("pat", "password");
    ...
}

using (Smtp client = new Smtp ())
{
    client.Connect("smtp.mail.me.com");
    client.StartTLS();
    client.UseBestLogin("pat@icloud.com", "password");
    ...
}

' VB.NET

Using client As New Imap()
	client.ConnectSSL("imap.mail.me.com")
	client.UseBestLogin("pat", "password")
	...
End Using

Using client As New Smtp()
	client.Connect("smtp.mail.me.com")
	client.StartTLS()
	client.UseBestLogin("pat@icloud.com", "password")
	...
End Using

AOL supports access via IMAP, POP3 and SMTP protocols. Below you can find the configuration settings for all protocols.

All AOL servers (IMAP, POP3 and SMTP) can work in plain mode (you can use Connect method) or use implicit SSL (use ConnectSSL method) or use explicit SSL (you can use Connect method and then secure the channel using StartTLS or STLS methods)

IMAP

Server: imap.aol.com
SSL: true-implicit
Port: 993 (default)
User: pat@yahoo.com

POP3

Server: pop.aol.com
SSL: true-implicit / true-explicit
Port: 995 (default) / 110 (default)
User: pat@aol.com

SMTP

Server: smtp.aol.com
SSL: false / true-implicit / true-explicit
Port: 587 (default) / 465 (default) / 587 (default)
User: pat@aol.com

Following are the code samples for Mail.dll .NET IMAP, POP3 and SMTP component.

// C#

using (Imap client = new Imap())
{
    client.ConnectSSL("imap.aol.com");
    client.UseBestLogin("pat@aol.com", "password");
    ...
}

using (Pop3 client = new Pop3())
{
    client.ConnectSSL("pop3.aol.com");
    client.UseBestLogin("pat@aol.com", "password");
    ...
}

using (Smtp client = new Smtp ())
{
    client.ConnectSSL("smtp.aol.com");
    client.UseBestLogin("pat@aol.com", "password");
    ...
}

' VB.NET

Using client As New Imap()
	client.ConnectSSL("imap.aol.com")
	client.UseBestLogin("pat@aol.com", "password")
	...
End Using

Using client As New Pop3()
	client.ConnectSSL("pop3.aol.com")		
	client.UseBestLogin("pat@aol.com", "password")
	...
End Using

Using client As New Smtp()
	client.ConnectSSL("smtp.aol.com")
	client.UseBestLogin("pat@aol.com", "password")
	...
End Using

You can find more details about using implicit and explicit SSL or TLS with email protocols:

• Using SSL with IMAP
• Using SSL with POP3
• Using SSL with SMTP