Please help us help you and fill where relevant:
LimeSurvey version: Version 3.17.1+190408
Own server or LimeSurvey Cloud:
Survey theme/template:

Hello everyone,
I have an issue with the email delivery through LimeSurvey.

Emails sent by LimeSurvey as part of a project are ending up in the junk folder of our project partner or are being filtered out even before reaching the inbox, despite the sender being marked as trustworthy. According to the IT support of our project partner, the problem arises because the actual sender address and the specified sender address do not match. LimeSurvey sends emails on behalf of name@companyname.com, but the emails actually originate from LimeSurvey servers.

Is it possible to adjust the sender address in LimeSurvey so that it matches the actual sender address of the LimeSurvey server? I hope this will ensure that the system recognizes the emails as authentic and does not mark them as spam.

Or are there other solutions to solve this problem?

Many thanks in advance!

PS: I know my company is using a very old version, they finally upgraded to a more recent one, but this survey has already been activated.

but the emails actually originate from LimeSurvey servers.

If you are hosting yourself, the emails will definitely NOT come from the servers of the Limesurvey project, but from your servers. But I assume this is what you want to say.

So what are your settings for sending emails on this server and in this survey?

And yes, your version is ancient. Over 5 years without an update...