is your email on a blacklist?

https://mxtoolbox.com/blacklists.aspx

completely royalty free, free images for commercial or other use

https://unsplash.com/

HTML meta tags checker for SEO

https://smallseotools.com/meta-tags-analyzer/

open graph facebook tags checker

https://developers.facebook.com/tools/debug/

useful analysis of SEO on web site

https://app.neilpatel.com/

testing your computer and browser for 3d speed or power

https://www.wirple.com/bmark/

Keyword search volumes for a particular keyword

keyword volumes
https://www.wordtracker.com/search?query=metal%20home

comparing popularity of searches
https://trends.google.com/trends/explore?geo=US&q=barndominium,metal%20home

see your google adwords ad

http://www.google.com/AdPreview

using google like a pro

https://resources.spyfu.com/master-list-every-google-search-operator-40-how-to-use-them/?c=7&g=3

custom email apps and receving emails with user@domain.com via subdomain.domain.com

Remove "via" information from emails not sent through Gmail

Gmail checks whether the messages you send are authenticated.

• If you send messages using a bulk mailing vendor or a third party affiliates, check out Gmail's Bulk Senders Guidelines, including: Publish an SPF record that includes the IPs of the vendor or affiliates which send your messages.
• Sign your messages with a DKIM signature that is associated with your domain.
• Make sure the domain in the "From:" address matches the domain you're using to authenticate your emails.

Emails can be authenticated using SPF or DKIM.

SPF specifies which hosts are allowed to send messages from a given domain by creating an SPF record.

DKIM allows the sender to electronically sign legitimate emails in a way that can be verified by recipients using a public-key.

check h1 tags on a web site

https://www.seoreviewtools.com/html-headings-checker/