Email not delivered to gmail addresses

Questions
1

Silverstripe Version:
Silverstripe 4.10
Question:

I have an enquiry form that sends an email to zxc.example.com with the details filled in the form and a thank you email to the sender and it works for most cases but won’t deliver either mail if the email is of @gmail.com.
Any clues on solving this?

// Include any relevant code. If you have a lot of code, link to a gist instead.
2

Could be a number of different things. Start by checking:

  • Do you have a sender address configured on the site, from a real domain
  • Do you have SPF / DKIM records for the site’s domain which indicate that your server is authorised to send emails from that domain
  • Could the subject line of the email be interpreted as being spammy
3

Thanks for the response.

  • Yes, the sender address is from a real domain.

  • Will check this one out.

  • Will check this as well as the mail does end up in spam sometimes, but wouldn’t the mail just be sent to the spam folder if the subject line is interpreted as spammy or could it block the delivery completely as well?