"eboltz" == eboltz <eboltz@lhtservices.com> writes:
eboltz> Mark, I tried using that, but it doesn't overwrite the eboltz> sender_canonical_maps settings and with that disabled the eboltz> emails don't route at all.
eboltz> Here is one of the error messages that I get
eboltz> 550-From header sender domain not verified Verified Senders eboltz> page 550 verify the sender domain or email to be allowed to eboltz> send _______________________________________________
This means that you don't have SPF records set up for your system, or they're set up incorrectly.
It's the 'sender domain' that needs to be verified. You may also ned to set up SRS (Sender Reriting Scheme); but IIRC MM3 rewrites sender addresses anyway.
I suggest something like https://mxtoolbox.com/SPFRecordGenerator.aspx to help you generate a working TXT DNS record that will remove another a barrier to getting email through.
It can also help to debug if you gave a gmail account, and try to send email to it from an address using the domain of your list. Either it won't arrive at all with a similar SMTP-time error or you'll find debug info in the headers of the received email.
Peter C