Google Recently updated their Mail Security Policy. This has effected millions of users World Wide who rent from a hosting Company and does not use any Google Services.
Your Email to a Gmail user or G-Suite user will bounce back with a message below:
This is the mail system at host server327.xenserve.com.
I’m sorry to have to inform you that your message could not be delivered to one or more recipients. It’s attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system
<email@example.com <mailto:firstname.lastname@example.org> >: host aspmx.l.google.com[2a00:1450:400c:c07::1a]
said: 550-5.7.1 This message does not have authentication information or
fails to pass 550-5.7.1 authentication checks. To best protect our users
from spam, the 550-5.7.1 message has been blocked. Please visit 550-5.7.1
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.1 information. m63si959779wma.121 – gsmtp (in reply to end of DATA
You will need to re-send this E-mail within minimum of 20 min to 1 hour, this have a 80% chance of getting through on the second attempt. If not, mark this email and try send it again in the 3rd attempt.
Create a Gmail account (Free) and send the E-mail from there, make sure you create an Auto Forwarding Policy within G-Mail so replies to your G-Mail account will automatically be forward to your email@example.com Account
Ask your Customer/Supplier to add your E-Mail address to their CONTACT List, see below How:
Open Contacts in Gmail.
Tip: Click Gmail, for example, near the top left corner and select Contacts from the menu that appears.
Start typing the contact’s name or email address in the search field.
Use auto-completion to select the desired contact.
Hint: If Gmail does not suggest the contact for which you are looking, click the desired entry in the search results and hit Enter.
Make all desired changes or additions to the contact’s sheet.
Click Save now.
Unfortunately, there are currently very little we could do right now, as Google is acting as a big bully to force people either sign up to a free GMail account or a paid Premium G-Suite Services
We will keep you Updated on this matter