Somebody just gave you their email. Right now they remember who you are. Three days later they do not, and your welcome email arrives to a stranger.
Not an hour, not tonight. The person still has your tab open. If your tool only processes automation once a night, that entire decision is being made for you and you should find out today.
A welcome series is not a course. Email one says what happens next. Email two shows the single most useful thing you have. Email three asks one small question. Anything after that belongs in your normal schedule.
The first is opened out of curiosity. The second has to earn its place, and most second emails are the first one again with a different subject. Split on whether they opened. People who did get depth, people who did not get the same message once more with a new subject line.
A reply teaches your sending reputation that people want your mail, and it starts a conversation a sales person can continue. A click teaches an analytics dashboard something.
This is teaching material and our own reading of standard practice, not advice for your specific setup. Check anything important with your own specialist.
Write what is happening. We reply with what to fix first and why. No call, no pitch.