Incoming IMAP server host name is mail.onetel.com and port 143
Incoming POP server host name is pop.onetel.com and port 110
Outgoing mail use smtp.onetel.com and port 25
No encryption is the correct setting for this domain so if using TLS or SSL those settings need to be removed.
If you don't have the settings as above you'll have problems collecting your mail.
Please log in to My Account if you need to view or pay your bill, manage boosts and track your usage. From My Account you can also check your connection and test your line for any issues in the Service Centre.