Sometimes, email addresses may appear instead of sender names when an email is sent.

SMTP emails may not display the sender's name if the email provider does not recognize the sender or considers the email unsolicited. Some email providers will only show the sender's name after the recipient has interacted with an email, deeming it 'safe'.
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Therefore, if it's the first time you're receiving an email from a sender, the sender's name might not be displayed until you interact with that email.

The observed behaviour is intentional from Gmail to protect users from initial outreach.

Especially with B2B inboxes, when they receive an email for the first time from a new external domain, they will 'sandbox' until there was positive engagement.

In most cases this will be a reply. From that point on, Google trusts your emails as you have demonstrated to be a trusted sender with your new domain and all new emails will be rendered properly.

Sometimes, you might circumvent this behaviour by building up good domain reputation with Google.

The best way to circumvent this sandboxing is by building up domain reputation (which you can either get through prolonged warmup or good & targeted cold email campaigns). 👍🏻