Unable to send email to some domains, such as Hotmail, Yahoo, Gmail etc.


This article provides troubleshooting information for sending to large email providers such as Hotmail, Outlook.com, Yahoo and Gmail that may temporarily delay or reject your inbound message. These providers may also mark your email as junk or indicate that the sender is not authenticated. For example, Gmail may display a question mark for the senders avatar.


The most common reason for mail not being accepted by servers such as Hotmail, Yahoo, Gmail, AOL, etc. is due to a temporary delay or rejection. The causes for these are varied but normally a bounce message will be generated indicating that the sent message was either delayed or could not be delivered along with an SMTP error code that the remote server generated during the SMTP transaction. The error code that is returned in the bounce should also be logged within the MailEnable SMTP log files. Usually the large email providers will also provide a URL that can assist in troubleshooting the SMTP error and provide detailed information relating to the delay/rejection.


Here are some troubleshooting guides from the various providers that contain detailed bounce errors and links to articles to address each of them:

Gmail: https://support.google.com/a/answer/3726730?hl=en

Outlook.com: https://mail.live.com/mail/troubleshooting.aspx

AOL/Yahoo: https://postmaster.verizonmedia.com

Below are some best practices that need to be implemented within MailEnable to prevent delays and rejections from remote mail servers:

Product:MailEnable (All Versions)
Class:PRB: Product Problem or Issue
Created:31/01/2002 2:22:00 PM
Revised:Monday, January 11, 2021