What is the best tip for increasing email response?

1) Personalization; 2) Timezone (be sure it's not early morning or deep night when you send a message); 3) Cool subject; 4) Professional signature; 5) Clear call-to-action.

Email signature - if I see that a person takes it serious about their branding, I would respond. I also want to for example check their social media or website before replying - and that would be easier to do if they had links in their email signatures.

send emails at different times based on time zones

Depends on the context? If you are cold emailing people it is a numbers game. Make sure your email is short enough for the person to read, and your CTA is easy for them to say yes to.

Building credibility.

Here are my top five tips for writing an email that people actually want to open: 1. Make it personal. Don't just blast out an email to everyone. Put in a little time to personalize the message. Use the recipient's name, mention something you know about her, and so on. 2. Keep it real. Email doesn't offer much opportunity for emotion. So you have to be more creative. Offer helpful information the recipient can use right away, provide interesting information, or let the reader know you care. 3. Use a subject line that will make the recipient curious. 4. Keep it short. Most people don't have time to read long emails. 5. Give the recipient a call to action. Tell them exactly what you want them to do, and offer a reward for doing it.