Thanks for your update here.
I read all your descriptions above carefully and got some personal ideas, please check the information below and see if they could help:
- To firstly confirm if there is something wrong with this specific usual email account, please try to log in your web mail or the two other Outlook 2010 clients and check if it could send and receive normally there.
- If it indeed could work fine on the two Outlook 2010 clients, then we need to check if the account settings we set on your Outlook 2019 client are proper.
We could get the correct configuration information from those two Outlook 2010 clients(File > Account settings > Account Settings > Email > Select your email account > Change > More Settings). Then, compare with your settings in Outlook 2019 and see if there is any difference. Make sure you have already use the same account settings to avoid possible issues. - If the issue still continues, then we might could infer that the issue is more related to this specific Outlook 2019 client. As I know, Firewall and Antivirus program in your Windows might will block your connections to your mail server, it is suggested for you to reboot your Windows in safe mode and only run Outlook 2019 alone to test and check how is the issue going.
- By the way, have you tried the same tests in other Outlook 2019 desktop clients yet? As I know, different mail servers have different support for different versions of Outlook client. For example, some old exchange servers could not support newer Outlook versions like Outlook 2019. To confirm if this is your issue, you could try to configure the same email account to other Outlook 2019 clients and see if there is any differences.
Any update, please feel free to post back.
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