Follow these steps to verify if you have published the correct Vtiger DKIM record in the sending domain correctly:
- Visit the following website, https://mxtoolbox.com/dkim.aspx.
- Enter your sending domain name.
- Enter the following in the Selector field - vtigermail.
- Click on DKIM Lookup.
- For example, refer to the screenshot below.

- Lookup results should display that all three DKIM checks have been cleared. Refer to the screenshot below.

Note: In Vtiger, DKIM is mandatory for both Email campaigns and Ad-hoc emails.