I never used exim. My faviorate MTA is postfix. But this time I needed to configure exim MTA (mail transfer agent used in Unix-like operating systems) to router all mails using a smarthost called mta3.somewhere.com
Open exim configuration file i.e. begin routers section and add or modify it as follows:
driver = manualroute
domains = *
transport = remote_smtp
route_data = "mta3.somewhere.com"
Restart exim to take effect.
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