SPF fail for alias domain

Hi all!
I have 2 domains hosted at gmail, let’s say “zxc[.]net” and “zxc[.]com”, the second being an alias of the first. DMARC reports I receive for zxc[.]net say everything is fine, but reports for zxc[.]com say that spf “fail-unaligned” because (if I correctly understand it) when I send mail from and address at zxc[.]com, smtp header says “zxc[.]com” but HELO command says “zxc[.]net”.
Does anybody know if it’s possible to configure SPF record to accommodate this situation?

Kind regards

SPF is only checked against HELO if the mails doesn’t contain a Return-Path header. If Return-Path is present, it will be used for SPF check and therefore you need to look into, how you align your Return-Path with your “From: Domain”. Keep in mind that SPF can be perfectly valid, while still being unaligned from a DMARC perspective.
Regards
/Uffe

Thanks for your tip! I’ll try it.

Kind regards

@UffeA’s feedback is mostly correct, but with a common misconception.
SPF checks do NOT perform against the ‘Return-Path’ header. They are performed against the value of the mail-from SMTP element. The Return-Path header appears amongst headers of messages simply to reflect what the mail-from was, and each hop that the message transits can change the Return-Path header value based on what actually happened during SMTP.

A source of confusion on this topic is that some people call the mail-from ‘returnpath’ interchangeably. (also ‘bounce address’, ‘rfc5321.from’, ‘rfc5321.mailfrom’)

So to resolve the stated issue, you must update the sending behaviour to actually use the same domain in mailfrom as appears in the From: header (rfc5322.From). To note, the mailfrom domain in use may be a subdomain of the From domain, so that you can usefully segregate SPF records. (This is assuming your DMARC record is set with relaxed alignment, which is the default behaviour)
e.g.
mailfrom value of tomki@support.dmarcian.com
From value of tomki@dmarcian.com

Use of a subdomain this way would mean that you must have a specific SPF allowance at the DNS TXT location for support.dmarcian.com.

–Tomki

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Thanks Tomki!
The point is that the 2nd domain is not a sub domain of the 1st one: the addresses are me@zxc.com and me@zxc.net, both addresses belonging to the same organization.

So, you say I’ll not fix this issue making Replay-to equal to From?

Right, you cannot fix the issue by changing message headers. You must change sending server/application behaviour.
If you have correct DKIM signing on this traffic (DKIM key for the same domain as the From header), the traffic will still pass DMARC successfully.

You mean the HELO?

Should my problem be solved if both domains have the same DKIM signature?

@Tomki, I’ll agree that the myriad of names for rfc5321.mailfrom is confusing, but isn’t ‘common misconception’ a bit harsh?

An explanation for the many names can be found at https://dmarc.org/2016/07/how-many-from-addresses-are-there/