Can email spammers disguise the origin of their messages?

[Stephen Tashi]

TL;DR Summary

Can email spammers alter email headers to forge the ISP originating their spam messages?

Can email spammers alter email headers so that we can't find out which internet service provider and mail server originates their messages?

Sometimes emails sent from a reputable ISP get temporarily blocked by some servers due to complaints about spam originating from the ISP. The sender is referred to https://help.yahoo.com/kb/postmaster/SLN3434.html?guccounter=1

Do email providers other than Yahoo do such blocking? Have spammers devised ways to get around such blocking?

 

[anorlunda]

https://gbhackers.com/email-header-analysis/
https://support.google.com/mail/answer/50200?hl=en
Google gmail seems to define spoofing email as dealing with mail falsely appearing to come from you. For incoming email, they call it forging:

https://support.google.com/a/answer/2466580?hl=en

Gmail supports Domain-based Message Authentication, Reporting, and Conformance (DMARC) as a way to prevent this type of spam.

The war between cyber attackers and cyber defenders is endless. Compare it with the war to stop money theft and fraud. Thousands of years of human experience has not produced a foolproof way of preventing that.