We use Gmail as our mail servers but that's a different domain than tgd-inc.com. A few days ago I got a bounce since our domain doesn't have a DNS SPF record, which basically says that for our domain mail from these servers are fine.

I sent an email to my Yahoo account and the header has:

Return-Path: 
Received-SPF: none (domain of tgd-inc.com does not designate permitted sender hosts)
Authentication-Results: atlas315.free.mail.ne1.yahoo.com;
 dkim=pass header.i=@tgd-inc-com.20230601.gappssmtp.com header.s=20230601;
 spf=none smtp.mailfrom=tgd-inc.com;
 dmarc=unknown header.from=tgd-inc.com;

I did an nslookup to see what Google has set up (v=spf1 is the line we want).

% nslookup -type=txt google.com 
;; Truncated, retrying in TCP mode.
Server:		8.8.8.8
Address:	8.8.8.8#53

Non-authoritative answer:
google.com	text = "facebook-domain-verification=22rm551cu4k0ab0bxsw536tlds4h95"
google.com	text = "docusign=05958488-4752-4ef2-95eb-aa7ba8a3bd0e"
google.com	text = "onetrust-domain-verification=de01ed21f2fa4d8781cbc3ffb89cf4ef"
google.com	text = "v=spf1 include:_spf.google.com ~all"
google.com	text = "docusign=1b0a6754-49b1-4db5-8540-d2c12664b289"
google.com	text = "webexdomainverification.8YX6G=6e6922db-e3e6-4a36-904e-a805c28087fa"
google.com	text = "apple-domain-verification=30afIBcvSuDV2PLX"
google.com	text = "google-site-verification=wD8N7i1JTNTkezJ49swvWW48f8_9xveREV4oB-0Hf5o"
google.com	text = "globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8="
google.com	text = "MS=E4A68B9AB2BB9670BCE15412F62916164C0B20BB"
google.com	text = "google-site-verification=TV9-DBe4R80X4v0M4U_bd_J9cpOJM0nikft0jAgjmsQ"

I added a tgd-inc.com DNS TXT record with "v=spf1 include:_spf.google.com ~all" then tried a test email. This is also what Google Workspace Admin Help says for SPF record and I guess that's how Dave has our stuff setup with Google.

Sent email to my Yahoo account and header looks good:Return-Path: 
Received-SPF: pass (domain of tgd-inc.com designates 209.85.210.178 as permitted sender)
Authentication-Results: atlas220.free.mail.ne1.yahoo.com;
 dkim=pass header.i=@tgd-inc-com.20230601.gappssmtp.com header.s=20230601;
 spf=pass smtp.mailfrom=tgd-inc.com;
 dmarc=unknown header.from=tgd-inc.com;

Here 209.85.210.178 is mail-pf1-f178.google.com.