(free) postmaster tools

Topics in this area:

enigma secure email

share your secrets via email - enigma is a secure, one-time use, passwordless link generator

inxbox temporary email

a ready-to-use mailbox that receives any message and keeps it for a limited time

inxsend fake smtp/api service

a fake smtp/api service with web gui for testing emails in applications easily

tester for spf and dkim

an online check tool to validate SPF and DKIM settings sending an email message