Unfortunately, today, there is no reliable way to ensure that an email has reached the recipient. Due to the growing number of emails that end up being spam, unwanted commercial offers, data capture emails, emails with viruses, spy emails, etc ... mail servers, in order to serve their users, have had to create filters to protect them and deliver only clean, polished mail.
This filtering process is done by computers that don't always get it right and is based on algorithms that supposedly learn from users' decisions. For example, if a user deletes or marks an email as spam, it is very likely that that domain of the email will be marked for the future. They also analyze the contents of emails, subject matter and many other parameters, such as the origins of IPs or their coincidence with the sender.
All this means that neither we nor almost anyone can ensure the reception of the same. There are certainly basic tips to avoid this as much as possible, for example, emails with senders such as admin@domini.com, info@domini.com, webmaster@domini.com, ie generic, are not advisable.
Emails from little-known or little-known servers are more easily blocked, so many times the same email sent from your email with your domain or sent from Gmail, Outlook, Hotmail, Proton, AOL, Zoho, iCloud, Yahoo, GMX ... have very different results.
At Homeprice we are constantly evaluating alternatives to avoid these effects, in fact, we offer the possibility of connecting to Hubspot to avoid it significantly since once connected to this service they are the ones who can send emails on behalf of and have very advanced algorithms to significantly increase email delivery. Hubspot offers free start-up plans that give you plenty of play.
We also offer the ability to set up your own mail server to send mail, thus preventing the sender of the mail from being different from the sender.
We also advise you to check that your public IP or domain is not blacklisted; you can check it at the following link: mxtoolbox