For the majority of our clientele, your mail server settings are very similar to your email itself.

For example - if your domain is "awesomewebsite.com" and your email is "This email address is being protected from spambots. You need JavaScript enabled to view it."

then, your mail server settings are as follows:

Incoming: mail.awesomewebsite.com
Outgoing: mail.awesomwebsite.com

There are a number of advanced features to adjust.
If your internet provider is Vianet - you'll need to change the default outgoing port from 25 to 587.

If you've been with us a long time, you may be using 1and1 Email Servers
As such, your servers are, for POP3 and IMAP:
POP:
Incoming: pop.ionos.com
IMAP
Incoming: imap.ionos.com
For Both POP3 and IMAP:
Outgoing: smtp.ionos.com

Otherwise- default ports apply:

POP Settings
Incoming POP SSL Port - 995
Outgoing SSL Port - 465
Outgoing TLS/STARTTTLS Port - 587

IMAP Settings:
Incoming IMAP SSL Port - 993
Outgoing SSL Port - 465
Outgoing TLS/STARTTTLS Port - 587


Link to Ionos Configuration