[MaryPalmer6]

One thing I always check first is whether anything changed before the issue started. Even something that seems unrelated can sometimes influence how mailbox providers evaluate your campaigns.

 

[Cynthia Lucas]

I don't think PMTA itself is necessarily the issue. I'd probably spend more time reviewing sender reputation and campaign performance before making any software changes.

 

[CynthiaCooley]

Deliverability has become much more challenging over the last couple of years. Mailbox providers appear to be placing greater emphasis on recipient satisfaction than ever before.