An outgoing mail server delivers your outgoing mail from your email address to the recipient's mailbox. Like any email service provider, IONOS operates its own servers.
The name of the respective provider is accordingly part of the server address of the outgoing mail server being used.
IONOS Webmail is already set up to use the appropriate outgoing mail server. If you use an email client other than Webmail, such as Outlook, Thunderbird, or Apple Mail, you must enter the address of the IONOS outgoing mail server.
This is the only way these programs can send outgoing emails from your IONOS email account.
Email is sent using the SMTP protocol, which is used to transfer emails from your email client to the server.
The IONOS outgoing mail server uses the address smtp.ionos.co.uk. Emails are received through an incoming mail server (imap.ionos.co.uk or pop.ionos.co.uk).