The following error message say that Gmail checked your forwarded email and found it to be SPAM
Subject: Delivery Failure
Could not deliver message to the following recipient(s):
Failed Recipient: myname@gmail.com
Reason: Remote host said: 550 5.7.1 information. a54si3234084qtc.355 - gsm
tpSMTP error from remote mail server after end of data:
550-5.7.1 [127.0.0.1] Our system has detected that this message is
550-5.7.1 likely suspicious due to the very low reputation of the sending
550-5.7.1 domain. To best protect our users from spam, the message has been
550-5.7.1 blocked. Please visit
550 5.7.1 https://support.google.com/mail/answer/188131 for more information. - gsmtp
If the email-sending domain's SPF record does not specifically allow yourdomain.com as an intermediary forwarder, then such forwarded-email will fail SPAM check and bounce. As it is not possible to control SPF record of 3rd party email senders, the correct way is to change your email-collection process to comply with current Anti-SPAM systems.
We recommend that you stop email auto-forwarding at yourdomain.com, instead at Gmail goto Settings >> Account and Import >> Check mail from other accounts >> Add a mail account and setup email-collection via IMAP by Gmail from yourdomain.com. As Google says at https://support.google.com/mail/answer/175365?sjid=16510488372932699960-AP#users and I quote
If you forward messages from other email accounts to your personal Gmail account, follow the recommendations in this section to help ensure messages are delivered correctly:
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