Mail forwarder returns "550 SPF Hard Fail"

I just created a 000webhost account. I parked my vyperhelp com domain (held by GoDaddy) and added mail forwarding. It appears to work OK, except when I send an email from my work medtronic com domain, I get the following error.

Can someone help me resolve this? I expect some other emails may not be getting through.

AARGH. I had to remove all of the “.” from addresses in this message to get past the stupid “newcomers can only place one link in a topic” rule.

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This is the mail system at host mail post 000webhost 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

<mat01mar@centurylink net> (expanded from <mat@vyperhelp com>): host
    mx centurylink net[205 219 233 5] said: 550 SPF Hard Fail: Domain
    medtronic com does not designate 153 92 0 94 as permitted sender. (in reply
    to MAIL FROM command)

Any ideas about this? When I look through the headers on the bounce message, I see this that looks important:

Authentication-Results: spf=none (sender IP is 148.163.152.7)
smtp.helo=mx0b-00204301.pphosted.com; medtronic.com; dkim=none (message not
signed) header.d=none;medtronic.com; dmarc=fail action=none
header.from=mail.post.000webhost.com;

I am not so much worried about mails from my own work email, but I am worried that other emails from others are getting bounced too. Is there any way I can know if this is happening?

Thanks.

So only when your work email sends an email to the forwarder does it fail?

I know some workplaces have strict policy on correctly setup and verified to and from mail servers and I know that sometimes 000webhost isn’t recognised to have the correct email procedure setup and so some email providers will refuse to send / receive email etc

I know that the forwarder fails when I send an email from work because I get a bounce back. How would I know if others are failing? That is my concern. Is there any way to know how many messages addressed to my address are being bounced?