Different providers have different spamfilters, different rules regarding html mails, attachment file size, use of tls, policies regarding exspired certificates, and might have different log in procedures, so yes, if there are problems the question which providers are involved.
Snake liver oil would be more powerful.
So - a modem?
telling others not to buy something from Trump’s buddies is verboten. Remember: it’s the President’s burden to interpret the law.