Emails sent from Thunderbird are being rejected by receipent servers but sending through webmail works, why?
When sending emails to certain receipents, the emails are NOT being delivered:
Example: Reason: There was an error while attempting to deliver your message with [Subject: "Georgia Eid Holiday Offer"] to godfrey@uranustravel.com. MTA p3plsmtpa12-04.prod.phx3.secureserver.net received this response from the destination host IP - 31.204.154.237 - 550 , 550 we do not accept mail from this address.
OR
Reason: There was an error while attempting to deliver your message with [Subject: "MR ANAND X 4"] to adam.wiberg@stromma.se. MTA p3plsmtpa11-05.prod.phx3.secureserver.net received this response from the destination host IP - 195.130.217.201 - 554 , 554 Email rejected due to security policies - https://community.mimecast.com/docs/DOC-1369#554
However, when sending to the same email addresses using the GoDaddy WebMail option, the emails are being successfully delivered. Hence, I am not sure what Thunderbird is doing that is making the receipent's incoming mail servers reject my email.
Wšě wotmołwy (1)
I would guess that your email provider's SMTP server, or your ISP's user IP address range are on one or more blacklists.
The webmail will be handled by a different machine, or via a separate address. Webmail is of little use to spammers so they don't try or want to use it and it doesn't become tainted by association with spammy mail. Hence your webmail is not blacklisted while your SMTP server or IP address are.
Both of the delivery failure notices hint that your messages are being rejected due to their origin and that means either your email provider's smtp server, or your ISP's user IP address pool. You really need to take this up with your email provider and/or ISP, but often it seems they don't really care, and will point to their webmail and say "that works, so why don't you use it?"
You might not get these problems if you used one of the big providers, such as yahoo, outlook, aol or gmail.