Setting up Mattermost Emails on GitLab Omnibus

Hi,
i installed GitLab Omnibus( 14.8.2-ee) and activated mattermost in gitlab.rb.
When i click the password reset in gitlab, i do get an email from Gitlab.

It does not work for mattermost, and from reading various sources (tutorials/bug reports) i am
under the impression, that mattermost needs an SMTP server while gitlab simply uses sendmail.
Is this correct?
Do i need to set up or connect to an SMTP service for/with mattermost, so that mattermost can send mails?
If so, is there such a service provided by gitlab omnibus, or do i need to set up a SMTP service?

Thanks in advance.

Ok, i found the setting in the docs:

• By local sendmail can be used by using Server Name 127.0.0.1 with Port 25

With this it works without any further tinkering.

Thanks for providing such a complete software package, i really would not like to have to set up an smtp