Multiple domains - multiple access

[nacesprin]

No.

Is there any way to use an additional domain as SMTP?

Hello. Is there any successfully way to use a second domain to use as SMTP server in order to supply it to my customers, instead of the original smtp server? I explain: I’ve installed a fully working box.domain.com, but I want to use box.mycustomerdomain.com as SMTP server. Could it be possible? If i use it as port 25 non SSL, obtain this error: Feb 20 10:33:58 miab postfix/smtpd[27004]: NOQUEUE: reject: RCPT from ns513574.ip-192-99-9.net[192.99.9.142]: 554 5.7.1 <myaddres@gmail.com>: Relay a…