Go to settings-technical-outgoing mail server
Create a new record with your credetials
Setup partner emails
How its work?
All Odoo mail, by default, is sent from a server whose email address matches the email address of the current USER's PARTNER.
For example, I have an Administrator user, he has a partner_id field (PARTNER) inside which there is also an email. So Odoo will search for an outgoing mail server with the same user as email parnter and will send it through it.
This means that if we have 3 users and we want to send mail from them, we all need to set the same email address, which will correspond to the same server.
If we want users to send email on their own behalf, you must specify their personal emails in the partners and then configure the server for each of them.
If we want to have all users (or rather their partners) different emails but send them on behalf of the same campaign, then out of the box such a mechanism is not provided in Odoo. But this can easily be customized by code.