Mantis does not delay e-mail sending.
The problem might be caused by your mail server.

I understand, but being a Mantis account through the web, what would be the next steps to solve this problem?

Thank you !

You have to contact the administrator of your mail server.

Thank You.

I checked with our provider and the problem is in the number of emails that Mantis is firing randomly.
In the logs the problem occurs since the beginning of this month, as we have a limitation of 50 emails daily is creating a bottleneck.
Like two periods of today's logs.
10:00 612 - 50 approved / 562 rejected
11:00 1382 - 50 approved / 1332 rejected.
How could they help us in this case?
Thank you.

emails that Mantis is firing randomly.

Mantis does not fire emails randomly, but sends emails based on your configuration.
Check your email configuration settings.

Juliano Aguiar,

This is not a bug or feature request for MantisBT (you are asking for help on how to configure the system and how to deal with mail server restrictions ).

Please use the forums to get support on customizing and using MantisBT (refer to http://www.mantisbt.org/support.php for links and further details).