I noticed that our Rails app gets error when attempting to create a user and it narrowed down to sending a registration email.
When I tried to manually test it it turned out that mail actually goes out but with huge delay. It takes 1 minute to process.
time echo test | sendmail firstname.lastname@example.org
real 1m0.170s user 0m0.008s sys 0m0.004s
These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.