My client uses Cox Business Internet as their ISP, and is very tied in to using Outlook to access their email. Their webserver and email server are currently hosted on Linode. These may be on the same Linode instance, or each on their own. There is also a database server on its own, but I do not think that enters into anything here (unless I'm wrong and somehow the email server is on the db instance...). I do know that email relies on Postfix.
I am a programmer, not a System Administrator. I have a client who wants me to be both. In the past, we've brought in folks who wore the SysAdmin hat, and that's how we reached the current setup. From my standpoint as a programmer, Linode has met my needs and the needs of the website.
The problem we have is that for some reason, the emails that they send silently fail to reach accounts of most gmail users and lots of att.com users. A secondary problem is that a lot of email seems to be tagged as spam. Our last SysAdmin contractor thought he had identified the problem with the failed emails as being something inhibited by Cox's support for sending via external servers. This sounds very fishy, but he had links to back up his claim. In any case, he thought he had resolved everything with his umpteenth iteration of changing settings between the site's email configuration, the specifics for the client's Outlook settings, and probably some stuff that I'm forgetting.
That was months ago. Then the client hit a downturn in business, and then COVID happened. Now, things are finally improving again. But the issues with sending email are back in full force. They do not want anything to do with the contractor we had previously, and have been pushing for me to move email off of Linode.
I am out of my depth here. From what I have described, would moving their email off of Linode and onto an external email provider solve the issue (and still work for an SMTP-based web-app sending emails)? Are there known problems around Linode and/or around Cox?
