Emails won't send when I try to send an email to a gmail account

My clients are having problems when they try to email to a gmail account.
This is the reply they are getting back.

This is the mail system at host

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 host[]
said: 550-5.7.26 This mail is unauthenticated, which poses a security risk
to the 550-5.7.26 sender and Gmail users, and has been blocked. The sender
must 550-5.7.26 authenticate with at least one of SPF or DKIM. For this
message, 550-5.7.26 DKIM checks did not pass and SPF check for
[] did 550-5.7.26 not pass with ip: []. The
sender should visit 550-5.7.26
Prevent mail to Gmail users from being blocked or sent to spam - Gmail Help for 550 5.7.26
instructions on setting up authentication.
o2-20020a817302000000b00589f5a9e862si994068ywc.493 - gsmtp (in reply to end
of DATA command)

I would appreciate any help please.

You need to ensure your email domain has an SPF record in place with the correct include values (as per these docs: Treepl CMS Hosted Email )

You can check what is being resolved on your domain with a tool like this:

Also, if they were previously on BC emails, ensure you no longer have the (or similar) value in the SPF record as this is no longer resolving and seems to be causing problems as well.

You can optionally contact Trepel Support for a DKIM record value to add to the email domain’s DNS. However, this is not required and as long as the SPF is correct it should pass Gmail’s checks.


Thank you Adam. I will try adding “v=spf1 ~all”

@Adam.Wilson – So if I’m hosting email with Treepl, it’s required (by Google) to have this spf:"v=spf1 ~all"

Even if I’m not using a gmail account to send domain/website email, I still have to have it on the domain for Google to allow email to be sent TO addresses?

Hi @g.davis
No, with Treepl hosted email you actually just need
If the CMS sends email on behalf of your domain (ie: autoresponders, workflows…) then you need to add

You would only include the if email hosting with Gmail (or perhaps if using other Google services that sent emails on behalf of your domain).

Other service providers, that send email on behalf of your domain, may also require you to add other include values in your SPF record.

For further details, what the SPF record and the includes are for exactly is explained in this article: Treepl CMS Hosted Email

@Adam.Wilson - That’s what I thought, but when I didn’t have the email (to a account) would bounce back. When I updated the spf record by adding the google one too, the message didn’t bounce back. Not sure why though…

1 Like

I added also otherwise they were bouncing back.