Ensure Proper Return Address is Used: By default, the WordPress mailer fills in the From: field with [email protected] and the From: name as WordPress.

source:https://macrogamers.net

This is fine if this is a valid e-mail address. For example, if your real e-mail is [email protected], your host should pass the email on for delivery. It will probably send your mail as long as yourdomain.com is setup to send and receive mail, even if wordpress is not a valid mail box. But if you set you real email as the From: address and it’s something like [email protected], the mail may not send because gmail.com is not a domain handled by the mail server.

soource:https://en.wikipedia.org/wiki/Main_Page

Treated as Spam: Your email message may have been routed to a spam folder or even worse, simply discarded as malicious. There are a couple measures you can use to convince recipient’s mail servers that your message is legitimate and should be delivered as addressed.

SPF: (Sender Policy Framework) This is the most common anti-spam measure used. If you are on a hosted system, there is a good chance your host has set this up for the mail server you are using. Have WordPress email you and check the message headers for evidence that the message passed the SPF check. You can get a message sent by following the Forgot Password link on the login page. To keep your old password, do not follow the link in the message.
If your system email failed the SPF check, you can set up the credentials if you have access to your DNS records and your mail server’s domain belongs to you. Check the return path of the email your system sent. If the mail server listed there has your domain name, you can set up SPF credentials. There are several how-tos on the Internet.

DKIM: (Domain Key Identified Mail) This system is also used. You can use both SPF and DKIM in the same message. Again, just as with SPF, you can check if your receiving mailserver verified your host’s domain key by examining the mail header. There is a fair chance no signature key was provided, indicating your host chose to not use this protocol. Also as with SPF, if you can edit your DNS records and the mail server belongs to your domain, you can set up DKIM credentials yourself. Some how-tos exist if you search the Internet.