Gmail has a feature which is both really useful and also really annoying. Gmail is just about the only mail server which follows the RFC for SMTP correctly and will discard duplicate emails based on the SMTP ID. Where this is good is were you are in a couple of groups (or mailing lists), both of which are sent the same email - you only see one copy. Also, when you use conversation view you never end up having two copies of your email.
However it’s really annoying and does not match real people’s expectations or work flow. I’ll give you an example. Let’s say there’s an important announcement you need to email out to one of your groups. So you mail it out and then.... well you’ve no idea if anyone actually received it. Not good.
Another scenario is you CC yourself in an email or send yourself and email to remind yourself to do something - the email may well never appear in your inbox. If you’ve not seen this problem then you are probably using a single domain with a single email address for your account, in which case the problem does not occur.
There are solutions or work-arounds to these problems. Which is why I made my video linked above in the title to explain them.
Another scenario is you CC yourself in an email or send yourself and email to remind yourself to do something - the email may well never appear in your inbox. If you’ve not seen this problem then you are probably using a single domain with a single email address for your account, in which case the problem does not occur.
There are solutions or work-arounds to these problems. Which is why I made my video linked above in the title to explain them.