The most common issue we encounter with setting up POP3 accounts, especially on iPhones, is that the automatic account creation wizards assume security protocols that do not match your sendmail server.
Your sendmail server uses password authentication on port 587 and does not use SSL or TLS.
Assuming you have an iPhone, and depending on which version of iPhone you have,
- Select 'Settings' from the home page
- Scroll down and Select 'Mail, Contacts, Calendars'.
- Select the email account to modify.
- Scroll down to 'Outgoing Mail Server' and click 'SMTP'
- Click on the 'Primary Server'.
- Make sure the slider is 'On' and enter the SMTP host name (as provided).
- Enter the username and password (as provided).
- Change 'Use SSL' to off
- Click on 'Authentication' and select 'Password' - then go back to the previous screen.
- Click on the 'Server Port' and change to 587
- Go back until you get back to the main 'Settings' page.