Vetter allows you to safely determine whether an email you wish to send will be marked as spam. This is done by testing the email against a network of real email accounts, and checking whether it ended up in inboxes or was spammed.
Mailsnag allows you to develop robust SMTP integrations while safeguarding against unintentional spamming of customers during testing on QA and Staging environments. Error and delay simulation helps you find unsafe code during testing.