hi 2Q, I'm not a tech guru, merely a person who knows where to look for answers!

However, it should be fairly simple to ask the people who provide your email - that is, the people who provide from2QandZQ@this-part-the-hosting-of.com (ie, the people who look after the email address you send business stuff from- perhaps the same people as the website domain?) and ask if they use ESMTP, rather than the older SMTP. (simple message transfer protocol)