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![Anna Ward](https://ph-avatars.imgix.net/1700652/original.jpeg?auto=compress&codec=mozjpeg&cs=strip&auto=format&w=48&h=48&fit=crop)
What happens to your emails after you hit the "send" button? Find out in the first ever webcomic about email deliverability—we promise you'll never look at your emails the same way again.
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Postmark Express
The only webcomic about the Wild West of sending emails
![Anna Ward](https://ph-avatars.imgix.net/1700652/original.jpeg?auto=compress&codec=mozjpeg&cs=strip&auto=format&w=48&h=48&fit=crop)
To bring more clarity and accuracy to SMTP responses, Postmark presents the SMTP Field Manual, a one-stop resource for understanding SMTP error codes from all the major inbox providers and spam filter services.
SMTP Field Manual
A collection of SMTP error codes from major inbox providers.