I have a Ubuntu server that has a few WordPress sites on it. The hostname for the server is set to something like: ip-xxx-xxx-xxx.internal. So when WordPress sends an email (via PHP, via sendmail) it uses that hostname in the EHLO command. This causes some mail servers to reject the email.
I can't change the hostname for the server, and each site needs a different hostname anyway, so need a way to set this per website. So I think that also rules out any php.ini changes or sendmail/postfix config changes.
I looked at WordPress plug-ins, but I think they all expect you to just use a different SMTP server (relaying), and that isn't what I want. I just want to use the current setup, but have it report the correct hostname for each site.
Hopefully this is something easy I just overlooked... site needs to go live tomorrow. Thank you!