It's important you ensure that you're able to send emails from Alto successfully, and that they don't end up in your recipients junk/spam folder. One way to improve email deliverability is to check that Alto is included in your domain’s SPF (Sender Policy Framework) records.
Alto uses a third party provider called SendGrid to send emails on your behalf. When you send an email from Alto, we pass the email to SendGrid and they are then sent from the SendGrid servers. When the emails are received by the recipient, their security software will check the validity of these e-mails. Due to the process of how these e-mails are sent, they can be perceived as spam mail as they are sent on behalf of the agent by SendGrid. To verify the email is genuine, a check is done against the agents domain TXT records, otherwise known as SPF (Send Policy Framework). If sendgrid.net isn't included on the SPF records, this will reduce the chances of your email being received by the intended recipient.
For more information on the steps you can take to add Alto into your SPF records and overall improve email deliverability, click here