Hi! ireaditall
I am new to this site, but I have more than 15 years of experience in software development using Delphi and I have experience in creating mailing clients in Delphi. So, I can create the demo application you've requested matching your specifications precisely.
I do not see potential issues, as both Gmail and Office 365 expose their interfaces to third-party mailer clients. I think 3-5 days will be enough for this job.
What about components to be used, both Synapse or ICS are OK, but I would recommend to stay with Indy, as this is compatible with all versions of Delphi. (Although, if you prefer something else it's OK.) I can use XE4, XE7 or Delphi 10.4.
Thank you,
Alex.