Emails not arriving when you use forwarders to @gmail.com accounts

Problem: Gmail blocks some forwarded emails

When a message is forwarded, the IP that delivers it to Gmail no longer necessarily matches the one authorised by the original sender's SPF. Delivery may depend on DKIM still being valid and on other reputation signals, so Gmail may reject the message or file it as spam.

Before putting a missing message down to this problem, check delivery tracking and the exact SMTP text. A message Gmail accepted and then sent to spam is not the same as one rejected during delivery.

You can identify this problem from bounce emails received from Gmail with the following error:

Our system has detected that this message is
550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail,
550-5.7.1 this message has been blocked. Please visit
550-5.7.1 https://support.google.com/mail/?p=UnsolicitedMessageError
550 5.7.1 for more information

Alternatives to forwarding

Until January 2027, a personal Gmail account that was already using Check mail from other accounts can keep downloading email over POP without forwarding it. Google stopped accepting new users of this feature after the first quarter of 2026 and will remove POP fetching in January 2027. Google is also announcing the removal of Send mail as for external addresses in January 2027 on its page for that feature. See also the notice about Gmailify and POP.

The following article explains how to set this up:

• Manage my email from Gmail without changing provider

As a lasting alternative, add your Hostsuar account directly to the Gmail mobile app or to a client that supports IMAP and SMTP, or use webmail. These options access the original mailbox and do not depend on how a forwarded message is authenticated.

What forwarding does not fix

Adding Gmail to your domain's SPF does not authorise the forwarding server to send on behalf of every original sender. Nor should you turn off your domain's DMARC to try to fix third-party messages.

A forwarded message can keep a valid DKIM signature, but changing the content or the subject can invalidate it. Mechanisms such as SRS or ARC help in certain scenarios; they do not guarantee that Gmail will accept any forwarded message. Keep the exact bounce and check the route before blaming every failure on SPF.

If you need reliable access to the same mailbox from several devices, use IMAP with the original provider and test sending and receiving separately. Do not delete the source mailbox while it is still receiving email you need to keep.