What SMTP authentication?
About a year ago we migrated our in-house email servers over to MXroute where we have had zero problems. Now I want to remove the last email server in our network, an outbound-only server that only relays email from 2 of our web sites and sends it along to the recipients' server. I want to remove that server and shift the sending of the site emails over to MXroute, who is already hosting their domain's emails. Each site already has MX, SPF, and DKIM records in DNS and they will be sending email using "From:" addresses in their domains, and they are whitelisted. Both sites are running on very "old but bulletproof" script code which lacks many standardized features. Doing this made me realize I am clueless (my normal state) on the authentication required for them to send thru MXroute; and either I blanked out in that section or just missed the issue in the MX docs.
Is generic Auth/POP sufficient authentication for these sites to send via MXroute SMTP? One site has that capability already, the other I'd have to code in for them but its feasible. If Auth/POP is not accepted what other authentication is available?