The pictures show iOS 27. On older versions the screens look slightly different, the entries are the same. These are all the details you need:

Host name (incoming and outgoing): mail.dotplex.com
Username: Your complete email address
Password: Your email password

The iPhone picks ports and encryption itself. All server details are listed under Server information.

Step by step

1. Open Settings and tap "Apps", then "Mail", "Mail Accounts" and "Add Account".

2. Enter your email address and tap "Next".

The Add Account screen with the email address entered

3. The iPhone shows a list of providers. Tap "Add Other Account…" at the very bottom.

The provider list with Add Other Account at the end

4. Tap "Mail Account".

The list with the entry Mail Account

5. Enter your name as recipients should see it, your email address, your email password and a description under which the mailbox appears on the iPhone. Tap "Next".

The New Account form with name, email, password and description

6. Leave "IMAP" selected. For both the incoming and the outgoing mail server, enter mail.dotplex.com as the host name, your complete email address as the username and your email password. Fill in username and password for the outgoing server too, even though the iPhone marks these fields as "Optional". Tap "Next". The iPhone verifies the details, which can take a moment.

The incoming and outgoing mail servers filled in while the iPhone verifies them

If you get an error message, check host name, username and password for typing errors.

7. Leave "Mail" switched on and tap "Save". You only need "Notes" if you want to sync your notes through this mailbox.

The last step with the switches for Mail and Notes and the Save button

8. The mailbox is set up and appears in the Mail app. In a new mailbox you will already find our welcome message.

The welcome message from dotplex in the Mail app

Cannot send mail

If the iPhone receives mail but cannot send any, the outgoing mail server is usually missing username and password. The iPhone marks these fields as "Optional", but sending through dotplex requires them. This is how you check the setting:

1. Open Settings and tap "Apps", "Mail", "Mail Accounts" and then your account. Tap "Account Settings".

Account Settings with the SMTP entry under Outgoing Mail Server

2. Under "Outgoing Mail Server" tap "SMTP" and then "mail.dotplex.com" under "Primary Server".

3. Enter your complete email address as the username and your email password. The remaining settings should look as in the picture: "Use SSL" on, authentication "Password", server port 587. Tap "Done".

The settings of the server mail.dotplex.com with username, password, SSL, authentication Password and port 587