What is the best time of day to launch an email marketing campaign?

One of the questions that most concerns email marketers is what is the best way to get the most out of their email campaigns. the best time to send an email marketing campaign. Generally, this question is about which day of the week and time of day is optimal for the best results in openings.
We analyse here the evolution of 5 different campaigns of 4 of the agency's clients, launched at different times of the dayThe aim is to see how users behave from the point of view of openings.
Industry: B2C Retailer
Time of dispatch: 08.30
Total openings: 33%
57.5 % of the openings occurred within 5 hours of dispatch.
40.52% of the openings occurred within 2 hours of dispatch.
From 09.00 to 10.00 -first hour- the peak of openings occurred (10,69%).
Openings decreased as the hours passed, although between 21.00 and 23.00 on the same day of dispatch and between 09.00 and 14.00 the following day there was an inflection in the trend.
 
Industry: Healthcare B2B
Time of dispatch: 12.00
Total openings: 21%
Within 5 hours of dispatch, 35.67% of openings occurred.
Within 2 hours of dispatch, 20.82% of the openings occurred.
From 13.00 to 14.00 -second hour- the peak of openings occurred (11,35%).
Openings decreased as the hours passed, although between 08.00 and 14.00 the following day there was an inflection in the trend.
 
Industry: B2C Retailer
Dispatch time: 15.00
Total openings: 61.6%
Within 5 hours of dispatch, 49.43% of openings occurred.
Within 2 hours of dispatch, 34.71% of the openings occurred.
From 15.00 to 16.00 -the first hour- the peak of openings occurred (19,99%).
Openings decreased as the hours passed, although between 20.00 and 22.22 and 07.00 and 12.00 the following day there was a reversal in the trend.
 
Industry: B2B
Time of dispatch: 16.00
Total openings : 61%
Within 5 hours of dispatch, 49.57% of openings occurred.
Within 2 hours of dispatch, 35.6% of openings occurred.
From 16.00 to 17.00 -first hour- the peak of openings occurred (23.37%).
Openings decreased as the hours passed, although between 07:00 and 12:00 the following day there was an inflection in the trend.
 
Industry: Food B2C
Time of dispatch: 21.23
Total openings: 38%
Within 5 hours of dispatch, 26.13% of the openings occurred.
Within 2 hours of dispatch, 15.53% of the openings occurred.
From 09.00 to 10.00 the following day -second hour- the peak of openings occurred (12,29%).
In the early morning of the following day, between 07.00 and 13.00, there was a new peak in openings.
Conclusion:
The best time to launch an email marketing campaign is between 07.00 and 10.00 in the morning. However, we see that campaigns that have performed very well have been launched in other time slots. This reinforces the idea that the main factor affecting openings is the quality of the database, that is, the degree of affinity and interest of users regarding the content sent to them.