To be more concrete, my company uses services such as Zendesk, Zoom, Zapier, and PayPal. For example, from Zendesk, we receive email with a "From" address of 'Zendesk Status' via [the alias for info@myCompanyDomain]. The email is addressed to an email address belonging to my company. We already know that Zendesk is one of our service providers, so there is no need for them to say "via". Why don't they just use their own email address? Note that the "Reply To" email address is set to status@status.zendesk.com.
Commonly it's because emails are not being sent from mycompanydomain's own SMTP server and via the service provider's own.<p>When setting up the service, account owners are required to setup DNS records that authorise the service providers SMTP server to send on behalf of mycompanydomain so that the emails don't get rejected or end up in the spam folder.