Just to clarify, Thunderbird uses the IP address that you provide. You provide that by providing server names of incoming server and SMTP server. And those IP addresses are owned by bluehost. SPF records are records that are placed on the server by the email host--Bluehost. However, the other possibility is that the SMTP settings you placed in Thunderbird are insufficient. That is, Thunderbird provides the opportunity to specify the required authentication required by the email host. I suggest you review your SMTP settings to see if they are in compliance with whatever is required by Bluehost.

Thanks for your clarifying response David. I have checked and my SMTP settings are what Bluehost requires. I am suspicious that Google is not describing the situation correctly. I think it is more likely that they are suggesting putting the IP address of the SMTP server in the SPF record. I tried to suggest that, but they said no, that is not what they are suggesting. Does this make more sense to you?

My first suggestion is to review your SMTP settings. Posting a screenshot doesn't guaranteed a fix, but it will let other eyes see it. You might also review the issue with Bluehost, but they're pretty good at what they do, so I'd be surprised if there is an SPF record error. Still, I would let them know.

Thanks for the ongoing help. I will pursue it from here. I appreciate your time.